Comparing the two most popular smartphones is never going to be easy, and when the manufacturers insist on keeping their release cycles several months apart it makes the process even more tricky.
Add to this the fact that all high-end smartphones are just about as fast, responsive and feature-packed as each other, and picking a winner is all but impossible. Nevertheless, here we compare the iPhone 5S with the Samsung Galaxy S4:
Look and Feel
An obvious comparison to draw between the Samsung Galaxy S4 and iPhone 5S is how, after several years of breakneck development, both manufacturers are slowing down the changes. We're well aware of Apple's year-on, year-off mentality of changing the iPhone's physical appearance every two years, interspersed with smaller 'S' updates - and with the jump from Galaxy S3 to S4, Samsung made a similar move as it hones in on a design language shared across its Galaxy range.
Retaining its aluminium back and chassis, the iPhone 5S is immediately the more premium of the two when compared to Samsung's use of shiny plastics with the S4. Having kept the same screen size, the iPhone 5S remains an inch smaller than the Galaxy S4 and as a result it's lighter and smaller in every direction, measuring 7.6mm thick - the same as the outgoing iPhone 5.
A unique feature for the iPhone 5S is it's fingerprint reader integrated with the Home button; it can be used instead of a PIN or password to unlock the phone, and can make buying content from the iTunes Store quicker, negating the need to enter your password.
Apple's iPhone 5S gets the same 4in, LED backlit display as the year-old 5, with a resolution of 640 x 1136 giving a pixel density of 326 pixels per inch (ppi).
This is an inch smaller than the 5in Galaxy S4, and as such the Samsung has a higher resolution - full HD, at 1080 x 1920 - and pixel density of 441 (ppi). Being AMOLED, the Samsung's display is very bright and has an excellent contrast ratio, but suffers from occasionally looking blown out and cartoonish - and it tends to give its interface a cool, slightly blue tinge.
Some will say the S4 is too big, and other will argue that the iPhone is too small - in reality, it is down to personal preference and whether you want a larger or smaller phone.
It's a similar story with performance - and a lesson in not judging a book by its cover. High-end smartphones are at a stage now where they are almost universally strong performers. There are a few disappointments - the Huawei P6 is bogged down in custom software, for example - but otherwise devices like the Galaxy S4 and iPhone 5S are as fast and responsive as you would expect them to be.
Compounding this is Apple's reluctance to enter a race of statistics. The company announced the new 64-bit A7 is twice as fast as the year-old A6, but the actual speed of the chip and amount of RAM were not given. The Galaxy S4's quad-core 1.6GHz chip and 2GB RAM may win on paper, but in the real world product design and camera performance have become more important than horsepower.
Picking one smartphone over another on grounds of processor speed and RAM may well be misguided, but pledging your allegiance to iOS or Android is a very different story - and more so than ever with the arrival of iOS 7.
The biggest software update in the iPhone's history, iOS 7 takes the existing operating system and gives it an entirely new design. Just about every icon and symbol has been changed, replacing skeuomorphic design (green felt in Games Center, torn paper in Calendar) with a clean, simple and 'flat' interface which is the brainchild of Apple's head of industrial design, Sir Jony Ive.
In the other corner we have Android 4.2.2 Jelly Bean with Samsung's TouchWiz UI over the top. On the face of it, the Galaxy S4 is broadly similar to the Galaxy S3, and both are recognisable to any Android user - but where Samsung has made itself stand out from the Android crowd is with its own additional software.
There's voice-activated assistant S Voice, fitness tracker S Health, translation tool S Translator, as well as a huge number of camera features - the ability to use both front and back cameras at once, or record video when taking a photo. All look good when demonstrated to potential customers, but we're unsure how many would be used on a regular basis.
One operating system isn't necessarily better than the other, but they are very different; Android is the more open and customisable option, while iOS is more restrictive but arguably more intuitive as a result.
We're yet to use the iPhone 5S's camera, but on paper we know that its 8-megapixel sensor is smaller than the S4's 13mp, and iOS 7's camera app has far fewer features for photographers to experiment with. But the new iPhone's larger f/2.2 aperture and 15% larger image sensor will help improve low-light shooting. Adding to this is the 5S's larger pixels, which take a page from HTC's UltraPixel book and produce higher quality images by capturing more light.
The 5S's camera also has auto image stabilisation and an auto-focus that is twice as fast as last year's iPhone 5, although we are yet to see how this stacks up against the Galaxy S4.
While the Samsung makes do with a single camera flash, the 5S has two which can adjust their colour and intensity for over 1,000 combinations - a feature Apple claims makes photos taken with the flash more natural.
The Galaxy S4's larger, higher resolution screen will be a deal-maker for some; others will prefer the iPhone 5S's aluminium construction over the Samsung's plastic, and while unique, a fingerprint scanner probably isn't enough to convince an Android fan to switch to iOS.
In truth, neither phone is a groundbreaking departure from the previous generation, capable of snatching users of one and encouraging them to buy the other; instead what we have here are two of the best smartphones ever made, both proving that the market has equally strong options whether your loyalty lies with iOS or Android, Apple or Samsung.