Because we haven't yet had the chance to properly test the iPhone 5S and iPhone 5C, we're basing this article purely on specs. We'll update the review as we do more testing.
iPhone 5S vs iPhone 5C: UK price
This we can cover off easily. The price for the iPhone 5S is as follows: the 16GB iPhone 5S will cost £549 inc VAT in the UK. The 32GB flavour will set you back £629 inc VAT, and the 64GB model a whopping £709 inc VAT. The iPhone 5C comes in lower, as befits Apple's first plastic phone since the 3GS. It comes in just two capacities - 16GB and 32GB - that cost £469 inc VAT and £569 inc VAT respectively.
For comparison purposes, the now retired iPhone 5 used to cost as follows: 16GB = £529, 32GB = £599, and 64GB £699.
iPhone 5S vs iPhone 5C: processor
Here's where things get really interesting. The iPhone 5S is the first 64-bit smartphone. It comes with an all-new A7 chip with 64-bit architecture. It also has what Apple calls an M7 motion coprocessor, which should mean a lot more apps that use motion-tracking, such as fitness apps. The iPhone 5C by contrast comes with an A6 chip - it's basically the iPhone 5 with a new coat. Without doing any further testing we can't honestly comment on how this will affect performance. But if the iPhone 5C performs like the iPhone 5 it will be fast for a premium smartphone. Here's hoping the iPhone 5S is an upgrade. Apple doesn't tend to say how much RAM it puts into its smartphones.
iPhone 5S vs iPhone 5C: storage
Storage is another differentiator. The iPhone 5C comes in 16GB and 32GB flavours, but the iPhone 5S matches that and goes all the way up to 64GB.
iPhone 5S vs iPhone 5C: design, build, dimensions
Another key area of difference is the design. The iPhone 5C is a radical departure for Apple. It is primarily made of plastic - the last to come with a plastic shell was the 3GS. And it comes in a variety of colours, five of them in fact. The iPhoine 5S by contrast is more in keeping with the iPhone 5's tone. It comes in three metallic shades, including a gold effect.
The iPhone 5S's dimensions are 123.8x58.6x7.6mm, and it weighs just 112g. By contrast the iPhone 5C measures 124.4x59.2x8.97mm and weighs 132g.
iPhone 5S vs iPhone 5C: features
The key difference in terms of features as according to Apple goes a bit like this: the iPhone 5S has a chip with 64-bit architecture, and iOS7 was built for that architecture. It also has a fingerprint identity sensor and what Apple calls a better, faster camera. But in many ways the two phones are similar...
iPhone 5S vs iPhone 5C: battery
Another hardware spec Apple never gives away, and for which we'll have to wait to tear down a handset, is battery life. But unusually for a tech company Apple's claimed battery life figures tend to be close to the mark (steps back, waits for 'fanboy' accusations...). Both phones have built-in, non-swappable lithium-ion batteries. And Apple says both batteries will last for the same time. Apple says the iPhone 5S and iPhone 5C will last for up to 250 hours on standby, and 10 hours of talk time. Web surfing is 8 hours on 3G, and 10 hours on LTE and Wi-Fi. Apple claims 10 hours for video playback and 40 hours audio playback, for the iPhone 5S and iPhone 5C.
As I said before, before testing I expect these to bear out. Apple has a habit of underpromising on one device in order to make the lesser device look better. It did this previously with the iPhone 4S battery life, so that when the more powerful (but more power hungry) iPhone 5 came along it didn't look like a step back in terms of portability. So it is possible one will be better than the other, in this regard.
iPhone 5S vs iPhone 5C: cameras
Both the iPhone 5S and the iPhone 5C have two cameras, a front-facing FaceTime camera and a rear-facing camera known as an iSight camera. The specifications work out as follows.
The iPhone 5C iSight camera has and 8 megapixel sensor with ƒ/2.4 aperture and LED flash. It supports 1080p HD video recording at 30 fps with video stabilisation. There's a 3x zoom. The iPhone 5C's FaceTime Camera takes 1.2Mp photos at a resolution of 1280x960, and offers 720p HD video recording.
The iPhone 5S iSight camera has what Apple describes as a better 8Mp sensor, listing it as 8 megapixels with 1.5µ pixels. It has ƒ/2.2 aperture and a true-tone flash. The video capabilities are the same, as listed, as is the FaceTime camera.
We'll have to give both iSight cameras a good workout before we make a proper judgment as to whether the iPhone 5S' is 'better'.
iPhone 5S vs iPhone 5C: display
The screen is another area in which the iPhone 5C and iPhone 5S are eerily similar. Both have 4-inch (diagonal) widescreen Multi-Touch displays, with a 1136x640-pixel resolution that makes for a pixel density of 326ppi. Expect 800:1 contrast ratio and 500 cd/m2 max brightness from both the iPhone 5C and iPhone 5S.
iPhone 5S vs iPhone 5C: software
Both the iPhone 5S and iPhone 5C will launch with iOS7, and be upgraded for free to all new versions of Apple's operating system.
The similarities that match the iPhone 5C and iPhone 5S are in many ways as intriguing as the differences. They offer the same battery life and display, and broadly the same software experience. But the iPhone 5S is - we are told - quicker, with a better camera and some additional features. Whether that makes it worth the extra cash only you can decide.