Samsung Galaxy S3 - Android 4.0, TouchWiz
HTC One X - Android 4.0, HTC Sense
iPhone 4S - iOS
The argument of Android versus iPhone has been fought for the best part of five years now, and the two sides are just as passionate as ever. In case you've not read up on this ongoing debate before, Android is more open, more customisable and - usually - a fair bit buggier. Android 4.0 helps to lessen the gap on this front, but it's still roughly true.
A tinkerer can change how the phone behaves and looks significantly, without hacking the device. Apps from outside the official Google Play store can be installed easily too.
With an iPhone, you can't change any of this. You can alter background images, but that's about it - unless you hack the phone. The trade-off is that iOS has a much better selection of apps and games available. There are loads on Android too, but they don't reach the same heights in most fields as iOS.
What about the custom UIs of the Android phones? HTC Sense and TouchWiz have been used in HTC's and Samsung's phones respectively for years, and each offers features not seen in vanilla Android. HTC Sense is a little better-looking, with greater character and clock widgets that have become iconic.
There are downsides to using these custom UIs, though. They slow down Android updates, because they have to be reworked each time a new version of Google's OS comes out. Try to fit one piece of software into another and you can bet bugs will appear all over the place.
Samsung Galaxy S3 - microUSB w/MHL, 3.5mm jack, microSD, Wi-Fi Direct, DLNA, Bluetooth 4.0
HTC One X - microUSB w/MHL, 3.5mm jack, Wi-Fi Direct, DLNA, Bluetooth 4.0
iPhone 4S - proprietary socket, 3.5mm jack, Bluetooth 4.0
Like many top-end Android phones these days, both the Samsung Galaxy S3 and HTC One X have rejected the miniHDMI port. You're not left high and dry for video output, though. The microUSB slots on these phones are MHL-compliant, meaning you can plug them into a TV and pipe across HD video and surround sound with the right cable.
These MHL cables never (in our experience) come bundled with the phones, but are available for well under £20 if you shop around. Samsung has also produced an AllShare dongle, to make piping content over Wi-Fi to any TV dead easy.
The iPhone is a little more constrained, predictably. You have to invest in an HDMI adapter to get video transmitted non-wirelessly, and the official one costs between £28 and £35. That doesn't include the HDMI cable, either.
Samsung Galaxy S3 - 8MP, LED flash, 1.3MP user-facing
HTC One X - 8MP, LED flash, f/2.0, 1.3MP user-facing
iPhone 4S - 8MP, LED flash, f/2.4, VGA user-facing
Is the megapixel war coming to an end? Maybe it's already over. The first 8MP phones were released four years ago in 2008, and yet we're still rolling along with similarly-specced sensors today.
It's not quite as simple as that, though. Manufacturers are starting to pay a bit more attention to the aperture of their sensors, which also has a big effect on image quality. In spite of using a very wide aperture for a phone, we found that the iPhone 4S was still a bit better than the HTC One X at capturing detail. We haven't yet had a chance to give the Samsung Galaxy S3's camera a proper going-over, so stay tuned for the full review.
Samsung Galaxy S3 - 2100mAh
HTC One X - 1800mAh
iPhone 4S - 1432mAh
The Android duo have much larger batteries than the iPhone. It's no surprise when they have to power much larger screens with many more pixels in 'em.
However, as with processor power, there's another factor to consider here - power management. Android is notoriously bad at power management, in part because it allows apps do get away with murder in the background when not being used, accessing all sorts of battery-sapping system functions.
The Samsung Galaxy S3 should fare better than most, 2100mAh being enough to hold out for almost two days of light-to-medium usage. There is a solution to increase any smartphone's battery life hugely, of course - switch off mobile data. But then your smartphone stops being quite so… smart.