iPhone Duo vs iPhone 18 Pro Max

Build and design

The Duo is a foldable with a hinge, an inner display that unfolds flat and an outer display for quick use. Unfolded it is just 5.2mm thick, folded it is 11.3mm thick, and it weighs 254g. That is only 5g more than the Pro Max at 249g, which is surprising for a foldable, though folded thickness is the real trade-off. The Pro Max, by contrast, is a single slab at 8.75mm thick, with no hinge, no crease concern and no folded bulk.

Durability is the open question for the Duo, as with any foldable, and hinge and inner-display longevity should be checked in long-term reviews before buying. The Pro Max is the safer, simpler design, with a familiar aluminium unibody and Ceramic Shield 2 front and back. If you want the newest form factor and accept foldable compromises, the Duo wins on novelty. If you want proven slab durability, the Pro Max wins.

Display and benchmarks

The Duo offers a 7.6-inch inner display at 1878 x 2670 and a 5.4-inch outer display at 1398 x 2034, both ProMotion and Always-On, with up to 3,000 nits in one listing. The Pro Max offers a single 6.9-inch display at 1320 x 2868, also ProMotion and Always-On. For reading, split-screen work and video, the Duo's inner display is larger, while its outer display is smaller and narrower than the Pro Max's main display for everyday use.

On benchmarks, both use the A20 Pro chip on 2nm, so no speed winner is claimed between them — a controlled side-by-side benchmark between the Duo and Pro Max was not reviewed. The Duo lists 12GB RAM, which should help multitasking on its larger inner display, while the Pro Max should be just as fast in single-app use. For gaming, the Duo's larger screen is more immersive, while the Pro Max's slab is easier to hold for long sessions.

Cameras and video

The Duo offers dual 48MP cameras, a Fusion main and a Fusion ultrawide, with no telephoto, plus a 12MP Centre Stage front camera. The Pro Max offers triple 48MP cameras, with a variable aperture main, an ultrawide and a telephoto, plus an 18MP front camera. That telephoto gap is the clearest camera difference, and it matters if you shoot portraits or zoom often. For everyday photos, both should be close, as both use Apple's Fusion main pipeline.

No controlled side-by-side camera test between the Duo and Pro Max was reviewed, so no photo winner is claimed beyond the hardware gap. On video, both offer Apple's ProRes and cinematic pipeline, though the Duo's inner display is better for previewing and editing on the phone itself. If zoom and portraits matter, the Pro Max wins. If you mostly shoot at 1x and ultrawide, the Duo is adequate.

Battery, software and price

Battery figures are not directly comparable, as Apple does not disclose mAh for either phone. The Duo is listed with claims up to 31 hours video on the inner display and 44 hours on the outer display in one comparison table, while the Pro Max is listed with claims up to around 30 hours general use and 43–45 hours video depending on variant. Those figures depend on which display is used, so do not treat them as a direct battery winner. For most users, the Pro Max will be simpler to predict, while the Duo's battery will vary with inner versus outer use.

Software is iOS 27 on both, though the Duo adds foldable multitasking and, in reports, a side Touch ID button instead of Face ID, while the Pro Max uses Face ID. Apple Pencil support for the Duo was reported with unconfirmed timing, so do not buy the Duo on Pencil claims alone. In the US, the Duo costs $700 more than the Pro Max at every tier, and the same $700 / £700 / €700-scale premium applies in the UK and Germany. US prices exclude sales tax, while European prices include VAT, so do not compare the headline numbers directly. The Pro Max went on sale September 18 in the US and Europe, while the Duo went on sale October 23 in the US, UK, France and Germany, with supply very tight and some orders delayed into January.

Verdict

Buy the iPhone Duo if you want a foldable that unfolds into a 7.6-inch display, on sale in the US from $1,999 (256GB) and in Germany from €2,299. Buy the iPhone 18 Pro Max if you want a simpler slab with a telephoto camera and a lower price, on sale in the US from $1,299 (256GB) and in Germany from €1,599. For most buyers, the Pro Max is the smarter buy — the Duo is for foldable enthusiasts.