But which of the two deserves your hard-earned pennies? We've pored over the two superphones and cogitated long and hard to see which wins out in terms of specs, camera and sheer desirability. Read on...
Design – more of the same
At this point, both Samsung and Apple are refining rather than innovating in terms of design – both companies have their design philosophies, and they're sticking to them.
For Samsung, that means the Galaxy S4 features the same plastic – sorry, polycarbonate – build as its predecessor – and although it still feels a bit lightweight and flimsy, it does mean that you can easily swap out the battery and add flip covers, should you so desire. At 130g, it's heavier than the iPhone – no surprise, as it's a considerably larger 136.6 x 69.8 x 7.9mm versus the iPhone's 123.8 x 58.6 x 7.6mm.
Apple, meanwhile, has stuck with the tried-and-tested aluminium and glass build of the iPhone 5, adding a new gold-and-white finish to the existing grey/black and silver/white editions. Look closely and you'll spot the new Touch ID fingerprint sensor in place of the familiar Home button – of which more below. The iPhone certainly feels more substantial in the hand, despite its 112g weight – though that's balanced out by the advantages of having a micro USB port as opposed to a Lightning connector, as well as the S4's replaceable battery and 64GB of expandable microSD storage.
As far as we're concerned, the iPhone 5S wins out here – it's a sleek and stylish pair of Jimmy Choos to the S4's dull but practical wellington boots.
More after the break...
Screen – bigger is better
The Samsung Galaxy S4 packs an impressive 5in 1080p Super AMOLED screen, delivering 441ppi pixel density and tucked behind Corning Gorilla Glass 3 for safety.
The iPhone 5S' screen is the same 4in, 1136x640px Retina Display found on both the iPhone 5 and the iPhone 5C. At 326ppi, it's impressive – but it's hopelessly outclassed by the S4's bigger, higher-resolution effort. Of course, gadgeteers with smaller hands may find that the iPhone's screen makes for more comfortable surfing than the S4's big display.
However, we have to hand it to the Galaxy S4 here – a 5in 1080p screen is pretty much standard issue on high-end phones. If you're buying on contract, you'll likely be hanging on to your next phone for two years – by which time the iPhone 5S screen is going to look very dated indeed.
Specs – Apple goes 64-bit
Apple doesn't publish detailed hardware specs, but the 5S reportedly packs 2GB RAM along with its new A7 processor – the first 64-bit smartphone processor. Don't expect a massive increase in speed as a result, though – the A5's ARM v8 chip architecture is likely more about future-proofing the iPhone and powering hardware like the Touch ID sensor than delivering an immediate performance boost.
The iPhone 5S also features a new M7 motion co-processor, which makes for more efficient power management while enabling constant motion tracking. So, expect a boost in battery life along with an array of new motion-sensing tricks – including health apps and contextual awareness. If you're in a moving vehicle, the iPhone won't try and connect to Wi-Fi networks, for example.
The iPhone's standout new feature is the Touch ID fingerprint sensor. You can unlock your phone by either clicking and holding the sensor, or tapping the power button and then the sensor. It'll store up to five fingerprints; at present it's only used as a security measure, but when (if?) Apple lets developers at it, it has a whole host of potential uses.
The UK Galaxy S4 packs a quad-core 1.9GHz Snapdragon 600 processor, rather than Samsung's own 1.6GHz octa-core processor – you also get 2GB RAM, a replaceable 2600mAh battery and 16, 32 and 64GB storage options (with support for an additional 64GB via microSD). Other features include NFC, an IR blaster and support for Air Gestures and Smart Scroll.
Once again, Apple's refused to integrate smartphone features that are regarded as industry standards – like NFC and microSD – into the iPhone, in favour of gambling on a potentially revolutionary technology. Like Siri, Touch ID could have a whole host of applications – but only if Apple lets developers use it, and only if it's properly integrated with apps. It's too early to tell at this point – so if you're buying a phone based on how you'll use its features right now, we have to hand this round to the S4.