Apple made it clear when announcing the iPhone 6S and iPhone 6S Plus that they were two different takes on a single general design, using the same processor, operating system and force-sensitive touchscreen technology.
So let's take a detailed one-by-one look at the specifications to find out whether the two smartphones are just resized versions of one another, or more distinct than looks suggest.
Dimensions and design
iPhone 6S: 138x67x7.1mm, 143g
iPhone 6S Plus: 158x78x7.3mm, 192g
Naturally, the 4.7in iPhone 6S is smaller and lighter than the 5.5in iPhone 6S Plus, which is actually quite heavy compared with other recent phablets. The 5.5in Huawei Mate S weighs 156g, for instance, while even the 5.7in Samsung Galaxy S6 Edge+ is only 153g. Notably, both are also slightly thicker than their iPhone 6 and iPhone 6 Plus counterparts.
To be fair, both handsets are quite well featured. They include Touch ID fingerprint sensors integrated into the Home button and are made from Apple's ‘Series 700' aluminium, an aerospace-grade metal which should prevent the bending problems of the iPhone 6. Size, therefore, is the only real difference to consider.
iPhone 6S: 4.7in 1334x750 resolution at 326ppi with 3D Touch
iPhone 6S Plus: 5.5in 1920x1080 resolution at 401ppi with 3D Touch
Apple's continued refusal to add an FHD display to the base iPhones makes this a big win for the iPhone 6S Plus, which has a much denser 401ppi despite the enlarged screen. Not that the iPhone 6S is likely to look poor, as 1334x750 is enough for a 4.7in display. Still, pictures, videos and web pages will undoubtedly appear crisper and more detailed on its bigger brother.
The extra 0.8in will also work well with the new multitasking view in iOS 9, where two apps can run side-by-side together similarly to the existing Android feature. The two apps won't be quite as cramped on the iPhone 6S Plus.
3D Touch, perhaps the biggest new feature, is supported across all iPhone 6S and iPhone 6S Plus models. It adds functions and actions to apps by distinguishing between soft and hard finger taps. For instance, a gentle ‘Peek' tap will preview the contents of an email straight from the inbox, while a stronger ‘Pop' gesture will fully open the message and enable replying or forwarding. It's a nifty feature with a lot of potential uses, so we're pleased to see it included in both smartphones.
iPhone 6S: 64-bit A9
iPhone 6S Plus: 64-bit A9
Apple has elected to use the same processor in both devices, the new A9 chip with an embedded M9 motion coprocessor. This isn't very surprising, as manufacturers rarely - if ever - bump up the processing power of phablet variants even when enlarging the screen size.
We're not sure of the clock speeds or RAM of the A9 APU, although Apple has made some pretty bold claims about its capabilities, stating it to be 70 percent faster than the A8 chip in CPU tasks and 90 percent faster in GPU tasks. However this translates into everyday performance, it will be the same for the iPhone 6S and iPhone 6S Plus.
iPhone 6S: iOS 9
iPhone 6S Plus: iOS 9
Both handsets will run Apple's newest iOS 9 mobile operating system at launch. The OS adds six-digit passcode support and two-factor authentication, plus redesigned apps which make use of the Metal API to run faster and drain less power.
This latter point will be especially useful for the iPhone 6S Plus to compensate for its bigger, battery-hungry display, but there's no need to pit them against each other in this case as the general experience will be identical across both handsets.
iPhone 6S: 12MP rear, 5MP front
iPhone 6S Plus: 12MP rear, 5MP front
Once again, the specs are the same: a 12MP rear-facing iSight camera and a 5MP front-facing FaceTime camera for the iPhone 6S and iPhone 6S Plus alike.
These are, at least, significant improvements to the 8MP and 1.2MP cameras.
iPhone 6S: Up to 14 hours' talk time
iPhone 6S Plus: Up to 24 hours' talk time
An Apple promotional video let slip that the iPhone 6S includes a 1,715mAh battery, but the iPhone 6S Plus' specific capacity has been kept more closely under wraps. Nonetheless, judging by Apple's stated battery lifespans for the two devices, the larger phablet seems to be packing a significantly beefier cell.
In addition to an extra 10 hours of talk time, the iPhone 6 Plus can supposedly manage 14 hours of HD video playback to the iPhone 6S' 11 hours. It's also claimed to last up to 16 days on standby, whereas the iPhone 6S, according to Apple, has enough charge only for 10 days.
The iPhone 6S Plus, then, sounds like the better choice for road warriors, or anyone who plans to subject their phone to ultra-intensive use.
iPhone 6S: 16GB, 64GB, 128GB, no microSD
iPhone 6: 16GB, 64GB, 128GB, no microSD
Once more, there's nothing separating the two devices here, with an identical selection of internal storage sizes.
We will say that it's somewhat disappointing that even the more sizeable iPhone 6S Plus couldn't find room for a microSD slot, although most people are likely to find plenty of space on all but the 16GB editions.
Even accounting for the dimension disparity, these are two extremely similar handsets. The larger, higher resolution display of the iPhone 6S Plus stands out as a key advantage, but not everyone will see it that way; after all, many prefer a compact design to a sprawling phablet.
The iPhone 6S is also far cheaper, if still pricier than most smartphone competitors. The 16GB edition will cost £539, for example, while the equivalent iPhone 6S Plus will be £619. This £80 difference is consistent across the 64GB and 128GB models.
Fewer pixels or otherwise, lower prices are as good a reason as any for the iPhone 6S to come out on top, particularly when there's so little else to compete on. But the slightly larger screen will swing it for some with the iPhone 6S Plus.
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