We've tested the iPhone Duo and iPhone 18 Pro Max — here's the phone you should actually buy

(Image credit: Future) It's been a big year for the iPhone, thanks to the launch of the all-new iPhone Duo. It's Apple's first foldable, and arguably the most exciting new iPhone for the past several years. By comparison the iPhone 18 Pro Max is the best traditional iPhone to date. But which one is the better iPhone?The iPhone Duo has a lot going for it, including the large foldable display, but it makes some compromises that we'd really like to see fixed. Meanwhile the iPhone 18 Pro Max has improved just about every aspect of what makes an iPhone an iPhone — but at the expense of its "wow" factor. Thankfully we have put both phones through the ringer in the Tom's Guide labs, testing everything that makes them tick.Here's what we learned about iPhone Duo vs iPhone 18 Pro Max, and which of the two is actually the best iPhone.iPhone Duo vs iPhone 18 Pro Max: Specs Swipe to scroll horizontally Row 0 - Cell 0 iPhone Duo iPhone 18 Pro Max Price $1,999 / £1,999 AU$3,499 From $1,299 / £1,299 / AU$2,299 Display 5.4 inches (Outer), 7.6 inches (Inner) 6.9-inches Refresh Rate 1-120Hz 1-120Hz Chipset A20 Pro A20 Pro RAM 12GB 12GB Storage 256GB / 512GB / 1TB / 2TB 256GB / 512GB / 1TB / 2TB Rear cameras 48MP (main), 48MP (ultrawide) 48MP (main), 48MP (ultrawide), 48MP telephoto (4x optical zoom) Front cameras 12MP selfie, Under display camera 18MP Center Stage Camera Battery 4,883 mAh 5,567 mAh Charging speed 60W (wired), 25W (wireless) 60W (wired), 25W (wireless) IP rating IP68 IP48 Size 117.8 x 84.1 x 11.3mm ( 3.31 x 4.64 x 0.44 inches) (Closed) / 117.8 x 164.6 x 5.2mm (6.48 x 4.64 x 0.21 inches) (Open) 163.4 x 78 x 8.8 mm (6.43 x 3.07 x 0.35 in) Weight 254 g (8.96 oz) 249 g (8.78 oz) Colors Night Sky, Star White Black, Silver, Glacier, Burgundy iPhone Duo vs iPhone 18 Pro Max: Price & availability (Image credit: Tom's Guide)The iPhone 18 Pro Max starts at $1,299 / £1,299 / AU$2,299, which gets you a model with 256GB of storage space. Additional storage is available for an extra fee, with 512GB costing $1,499 / £1,499 / AU$2,699, 1TB costing $1,899 / £1,899 / $3,499 and 2TB setting you back $2,499 / £2,499 / $4,699. The Pro Max has been on sale for several weeks, and currently has delivery wait times of two to three weeks.The iPhone Duo starts at $1,999 / £1,999 / AU$3,499 for a model with 256GB of storage. Higher storage options include 512GB at $2,199 / £2,199 / AU$3,899, 1TB at $2,599 / £2,599 / AU$4,699 and 2TB at $3,199 / £3,199 / AU$5,899.The iPhone Duo is technically on sale, but online retailers and carriers have delivery wait times pushing back towards the end of the year — and into 2027. It's possible some brick & mortar locations may have physical stock, but you'll need to check your local establishments to find out for sure.iPhone Duo vs iPhone 18 Pro Max: Design & Display (Image credit: Tom's Guide)The most obvious difference between the iPhone 18 Pro Max and iPhone Duo is the overall shape and look of the devices. The iPhone 18 Pro Max is a traditional looking iPhone with the same 6.9-inch display as the iPhone 17 Pro Max. This screen is covered in Ceramic Shield 2 glass, and has an anti-reflective coating to minimize glare.Sign up to the Tom's iGuide weekly newsletter with coverage on everything from product launches to software updates, this is your go-to source for the latest updates on all the best Apple content.Meanwhile the iPhone Duo has a foldable design, with a wider 5.4-inch display, and a larger 7.6-inch display that unfolds as you open the phone. This larger screen has a similar aspect ratio to the 4:3 design utilized in Apple's iPads.The outer display has the same Ceramic Shield 2 glass and anti-reflective coating. The inner display has a nano-texture matte display that minimizes glare, but also mutes some of the colors in a way a lot of people aren't used to.According to our testing the iPhone Duo is slightly brighter, with a maximum brightness of 2,558 nits. The iPhone 18 Pro Max is slightly dimmer with a maximum brightness of 2,326 nits. (Image credit: Tom's Guide)The iPhone Duo's folding nature means it is both thinner and thicker than the iPhone 18 Pro Max. When folded the phone has a thickness of 11.3mm / 0.44 inches, which is reduced to 5.2 mm / 0.20 inches when unfolded. The iPhone Duo, by contrast, is 8.8mm / 0.35 inches thick.The Pro Max is slightly lighter, with an overall weight of 249 grams / 8.78 ounces compared to the iPhone Duo's 154 grams / 8.96 ounces. That makes the Duo the heaviest iPhone has ever made.Both phones have IP68 water and dust resistance, and can handle being submerged in up to six meters of water for up to 30 minutes. The iPhone 18 Pro Max is an eSIM-only model in North America, but physical SIM cards are available in other regions. The Duo is only available with eSIM, regardless of where you buy one.One advantage the iPhone 18 Pro Max has is the inclusion of Face ID, though this does mean you lose a little bit of screen space to the Dynamic Island cutout. The iPhone Duo has a hole-punch camera on the outer display and a hidden under-display camera on the inner display.iPhone Duo vs iPhone 18 Pro Max: Cameras (Image credit: Tom's Guide)The other crucial difference between the iPhone 18 Pro Max and the Duo is the fact the Duo only has two cameras. Both phones feature 48MP main and ultrawide-angle lenses, though only the Pro Max model features the 48MP telephoto lens (with 4x optical zoom).It's also worth pointing out that, despite the similar resolution, the two have different camera lenses and hardware specs. This includes the lack of variable aperture which, at the moment, is exclusive to the iPhone 18 Pro and Pro Max.But hardware is one thing, how do these cameras actually compare? We put both through a 10-round camera face-off to find out — and here's a quick rundown. Image 1 of 2 iPhone Duo. (Image credit: Future) In terms of the main camera, there isn't a whole lot of difference, The two phones manage to capture pretty similar photos, with the same lighting and colors in most places. However the iPhone 18 Pro Max has stronger contrast and captures shadowy areas a little better. Image 1 of 2 iPhone Duo. (Image credit: Future) The same is true of the ultrawide cameras. Unless you're looking extremely closely, more than the casual observer ever will, there's nothing to really differentiate the shots from both phones. Image 1 of 2 iPhone Duo. (Image credit: Future) Again, selfies aren't that dissimilar, even though the Duo has a lower resolution 12MP camera — compared to the Pro Max's 18MP Center Stage lens. Both manage to capture a realistic image, and pick up the finer details pretty well.At 2x magnification the loss of the telephoto lens doesn't make a huge difference to the quality of the iPhone Duo's zoomed-in photos. No doubt thanks to Apple's 2x "optical quality" feature, which simply crops down a higher resolution image to simulate magnification. Image 1 of 2 iPhone Duo (Image credit: Future) Increase the magnification to 10x and you can see a much bigger difference. The iPhone 18 Pro Max performs so well that you wouldn't really suspect that this has been zoomed in quite so far. However, the iPhone Duo produces a shot that is blurry, pixelated, and missing many of the finer details that the Pro Max's camera had no issues with. Image 1 of 2 iPhone Duo. (Image credit: Future) We're back to even footing with the low-light shots, and despite the Pro Max having a slightly wider aperture, the photos from both phones came out pretty well. Both cameras preserved the details, and lit up the display with minimal noise and loss of quality.Overall, the cameras on iPhone 18 Pro Max and iPhone Duo are fairly evenly matched in every way except for zoomed-in shots. All the digital tricks in the world can't seem to make up for the fact that the telephoto lens is missing on the Duo. So, if you can't live without taking higher-quality zoomed-in shots, then the Duo is not for you.iPhone Duo vs iPhone 18 Pro Max: Performance (Image credit: Tom's Guide)There's very little difference in performance power, on account of the iPhone 18 Pro Max and iPhone Duo sharing the same A20 Pro chipset. However, in terms of raw benchmarking scores, the iPhone 18 Pro Max has a slight advantage in all three major categories: computing, graphics and AI. Swipe to scroll horizontally Row 0 - Cell 0 Geekbench 7 (single, multi-core) 3DMark Solar Bay Unlimited Geekbench AI 1.7 iPhone Duo 4,007 / 11,363 62.3 fps / 16,496 69,438 iPhone 18 Pro 4,022 / 11,543 61.93 fps / 16,288 69,245 iPhone 18 Pro Max 4,025 / 11,525 67.9 fps / 17,850 71,974 As you can see the iPhone 18 Pro Max managed a single-core score of 4,025 in the Geekbench 7 test, compared to the iPhone Duo's 4,007. That's not a huge difference, though the gap grows a little larger when you look at the multi-core results: The iPhone 18 Pro Max scored 11,525 while the Duo came in with 11,363.3DMark's Solar Bay Unlimited graphics test saw the 18 Pro Max record a score of 17,850 and an average frame rate of 67.9fps. Meanwhile the Duo was quite a bit lower with a score of 16,496 and an average frame rate of 62.3 fps. AI processing also had a rather large gap, with the 18 Pro Max scoring 71,974 in the Geekbench AI 1.7 benchmark. The Duo recorded a score of 69,438.It's worth mentioning that the iPhone Duo actually scored better than the smaller iPhone 18 Pro in the graphics and AI testing. This is worth bearing in mind if you want maximum performance, but were worried the Pro Max might be a little too big for your tastes.iPhone Duo vs iPhone 18 Pro Max: Software & AI (Image credit: Tom's Guide)Both iPhone 18 Pro Max and iPhone Duo run iOS 27, and have the same basic selection of software and AI features. The main feature of this is Siri AI, which is the upgraded assistant capable of more AI-heavy tasks than the Siri of old. This includes better understanding of your requests, and the ability to understand personal context that helps you specifically.iOS 27 also includes features like expressive voices for Siri, the adjustable Liquid Glass interface, Siri Mode on the camera, smart tab optimization in Safari, alongside AI powered editing features like Reframe, Extend and CleanUp. In other words, if the iPhone 18 Pro Max can do it, so can the iPhone Duo. (Image credit: Tom's Guide)The real difference in software is that the Duo has a new UI, designed to take advantage of the new screen sizes. This includes the ability to multitask with split-view apps, the first and only iPhone to do so, while also offering a taskbar on the right side of the screen. However a lot of work still needs doing to optimize the apps for those screens, which is not something Pro Max owners have to know about.The iPhone Duo also features some exclusive features, including the Smart Take camera mode that follows a single subject with the aid of AI. The recent iOS 27.2 update added stylus support from the Apple Pencil USB-C, which is another thing that isn't possible on any other iPhones.Still, for the most part, the software experience is similar enough that it doesn't make that much difference. Certainly not when it comes to deciding between those two price tags.iPhone Duo vs iPhone 18 Pro Max: Battery (Image credit: Future)It's unsurprising that the iPhone Duo does not have as strong a battery life as the iPhone 18 Pro Max. For starters the battery is much smaller, with 4,883 mAh to the Pro Max's 5,567 mAh. The foldable also has to contend with the fact that it has a much larger screen to power, which is going to drain the battery much faster when in use. Swipe to scroll horizontally Row 0 - Cell 0 Battery Life (Hrs:Mins) Battery Size (mAh) 15 minutes charge 30 minutes charge iPhone Duo 13:20 4,883 42% 66% iPhone 18 Pro Max 17:31 (New Test) 5,567 44% 77% Our battery life testing found that the iPhone Duo lasted 13 hours and 20 minutes, which is over four hours less than the iPhone 18 Pro Max's 17 hours and 31 minutes.The iPhone 18 Pro Max also managed to recharge slightly faster, despite the fact both phones support up to 60W charging speeds. The Pro Max regained 44% of its battery in the first 15 minutes, which rose to 77% after half an hour. The Duo, on the other hand, reached 42% after 15 minutes and 66% after 30 minutes — despite the fact it has a smaller battery.In other words, if you value battery life above all else, the iPhone 18 Pro Max is the phone to go for. It has the larger, longer lasting battery, and manages to restore any lost charge much faster than its folding sibling.iPhone Duo vs iPhone 18 Pro Max: Which should you buy? (Image credit: Future)Overall, there isn't a whole lot of difference between the iPhone Duo and the iPhone 18 Pro Max. It's true, the design of the two phones couldn't be more different, and the experience of using a foldable is completely different to that of a traditional phone. That said, from a user perspective, you're getting a lot of the same qualities and results from both phones.The iPhone 18 Pro Max does have better battery life and the all-important telephoto lens. Combined with the noticeably lower price tag, that's enough to sway people in that particular direction. More so when you remember that they're a lot easier to get hold of at the moment.The iPhone Duo has the benefit of being something new and exciting, alongside the fact the larger screen offers a lot more utility. It's a device that offers the same productivity benefits as a tablet, with stylus support and split-view apps. But the downside is that you have to pay a premium and make some sacrifices in the process — particularly the long wait to get your hands on one. Follow Tom's Guide on Google News and add us as a preferred source to get our up-to-date news, analysis, and reviews in your feeds. More from Tom's GuideNow is the perfect time for Samsung to release a cheaper Galaxy Z Fold 9 FE — and it's all because of iPhone Duo24 hours with the iPhone Duo — here are my 5 immediate takeawaysI’ve tested the iPhone Duo, Galaxy Z Fold 8, Pixel 11 Pro Fold, and Razr Fold — here’s the foldable phone I recommend Tom is the Tom's Guide's UK Phones Editor, tackling the latest smartphone news and vocally expressing his opinions about upcoming features or changes. It's long way from his days as editor of Gizmodo UK, when pretty much everything was on the table. He’s usually found trying to squeeze another giant Lego set onto the shelf, draining very large cups of coffee, or complaining about how terrible his Smart TV is.