What technology do they share? Find out in in our comparison below.
Apple iPhone 5S vs. Apple iPhone 5C: Build
The two phones couldn't be more different in terms of their look and feel. The iPhone 5S retains the classic good looks of the iPhone 5 and is available in three aluminum color combos - silver/white, "space grey"/black and gold/white. It has a premium polish that the plastic iPhone 5C, with its five bright color options, obviously lacks.
In terms of size and weight, the iPhone 5S is exactly the same size as the old iPhone 5 - a neat and stylish 123.8 x 58.6 x 7.6mm. Although there are only millimeters in it, the iPhone 5C is bigger in every respect - measuring 124.4 x 59.2 x 8.97mm. There's a more noticeable difference in the weight. The iPhone 5S is a mere 112g, while the iPhone 5C (with a reinforced steel structure hidden beneath the polycarb plastic) is 132g.
You'll also notice that the classic Home button on the iPhone 5S has been redesigned to incorporate a revolutionary Touch ID fingerprint sensor. A thin stainless steel ring now encloses the button - the iconic rounded square is gone. Around the back, the iPhone 5S also features a dual LED flash. The iPhone 5C doesn't. More on this later.
Apple iPhone 5S vs. Apple iPhone 5C: Display
As expected, both new iPhones feature the same 4-inch touch-sensitive Retina display that debuted in the iPhone 5. The resolution remains unchanged at 640 x 1136 pixels and, although the pixels per inch rating of 326 means that the screen is crisp and clear (iOS 7 looks fantastic), it lags behind rival phones with bigger screens and fuller HD resolutions.
Apple iPhone 5S vs. Apple iPhone 5C: Camera
When it comes to photo prowess, iPhones have been good, but never quite as good as Nokia's Carl Zeiss-equipped Lumia handsets. Rather than bump up the raw Megapixels to 13, the iPhone 5C makes a few improvements to the Apple designed lens - notably a new camera app that auto sets white balance, exposure and creates a dynamic local tone map each time you snap a photo. There are also live filters and video stabilization to reduce camera shake. Plus an improved backside illumination sensor in the 1.2MP front iSight camera, which should compensate for any poor lighting during FaceTime calls.
The iPhone 5S makes further improvements, adding a dual LED "True Tone" flash, a Sapphire crystal lens cover and 15% larger sensor (with an f/2.2 aperture) that lets more light in - the iPhone 5C and iPhone 5 have a f/2.4 aperture. Alongside the existing face detection and panoramic features, there's also a new Burst mode, which can snap 10 photos per second and intelligently pick the best one. Both phones feature 1080p video capture, but the 5S also includes a fun Slo-mo option. This shoots 720p video at 120fps so you can capture the finer detail of key moments.
Apple iPhone 5S vs. Apple iPhone 5C: Connectivity
Both new iPhones feature wider support for LTE, as well as 3G/HSDPA and CDMA2000 support. There's still no NFC in either iPhone, but wireless connectivity is well served with 802.11a/b/g/n Wi-Fi and Bluetooth 4.0.
Apple iPhone 5S vs. Apple iPhone 5C: Processor
Performance-wise, the iPhone 5C uses the same dual core Apple A6 CPU that appeared in the iPhone 5 that it replaces.
However, the iPhone 5S debuts the new A7 processor, a revolutionary 64-bit chip that Apple says offers twice the performance of the A6. Technical details on the A7 are sketchy, but it runs OpenGL ES 3.0 for fast, detailed 3D graphics and has an M7 motion co-processor, designed to monitor the various sensors in the iPhone 5S. Expect future fitness and health apps to take full advantage of this.
Apple iPhone 5S vs. Apple iPhone 5C: Software
Both phones come with iOS 7, but it's worth pointing out that the 5S will run a 64-bit version of Apple's operating system and should be twice as speedy. We've already noted that there's a new camera app and iOS 7 makes Pages, Numbers, Keynote, iMovie and iPhoto apps free of charge. The iPhone 5S also includes the Touch ID app, enabling owners to use the built-in fingerprint sensor to unlock their phone or to approve iTunes purchases with a simple press. Another revolutionary feature that's unique to Apple's new flagship handset.
Apple iPhone 5S vs. Apple iPhone 5C: Storage
As for storage, Apple hasn't chosen to venture into 128GB territory. So there's a familiar choice of 16GB, 32GB or 64GB iPhone 5S models, while the iPhone 5C is available in 16GB or 32GB capacities. Choose wisely. Unlike many rival Android phones, Apple refuses point-blank to include a microSD slot for iPhone owners to expand the default internal storage.
Apple iPhone 5S vs. Apple iPhone 5C: Battery Life
According to the specs, both phones will manage up to 10 hours of talktime, up to 250 hours on standby, up to 10 hours on LTE, up to 10 hours on Wi-Fi, up to 10 hours of video playback and up to 40 hours of audio playback.
Apple iPhone 5S vs. Apple iPhone 5C: Pricing
As expected, the iPhone 5S isn't cheap. Sign your freedom away on a two-year contract and the 16GB model will cost $199, the 32GB model $299 and the 64GB 5S $399. Compare this to the iPhone 5C on a similar two year deal - the 16GB model will set you back $99, while the 32GB version costs $199.
Apple iPhone 5S vs. Apple iPhone 5C: Early verdict
The iPhone 5S is easily the better of the two phones and it's no more (and no less) than we expected, considering Apple's iterative release policy.
If you were hoping for a bigger, higher resolution display or NFC, you'll need to wait for the iPhone 6. For now, the 5S is a souped-up iPhone 5. It impresses with its fingerprint recognition sensor and its all-new 64-bit A7 processor, which comes with an M7 co-processor that Apple undoubtedly have big plans for. A test-bed for a body monitoring iWatch? Only time will tell.