The Galaxy S3 will go head to head with the iPhone 4S when it's released on 30 May, representing the biggest threat to Apple's hegemony. Both smartphones have similar suggested retail prices at £499 for the 16GB models, which also makes them the most expensive mainstream handsets on the market.
The base 16GB models will probably do the most business, but the S3 can scale up to 128GB. The maximum internal storage is 64GB, but the microSDXC slot means that the storage complement in Samsung's flagship handset can be augmented by a further 64GB. The Galaxy S3 also comes with 50GB worth of Dropbox storage, free for two years!
The iPhone 4S, by comparison, also tops out at 64GB of internal storage, but thanks to Apple's need to keep its devices locked down, you won't be able to increase that. You do also get Apple's iCloud service thrown in, which allows you to keep your iPhone backed up to the cloud, making it easy to recover your data if you ever lose the phone.
As far as system memory goes, the iPhone 4S has 512MB while the Galaxy S3 doubles-down to 1GB.
The S3's larger 4.8in screen sports an impressive resolution of 1,280 x 720. While the iPhone's screen is smaller, it also results in a more manageable handset. Also, despite the iPhone's lower screen resolution - 960 x 640 - it's 3.5in size results in a higher pixel density of 330ppi, compared to 306ppi on the Galaxy S3.
Both displays are protected by Corning's Gorilla glass but use different technology. The iPhone 4S uses an IPS LCD while the S3 incorporates a PenTile HD Super AMOLED.
On paper, the iPhone 4S is no match for the raw processing power of the Galaxy S3. Both phones' chips are based on ARM's Cortex A9 but Samsung's Exynos 4412 has twice the number of cores, which run nearly twice as fast - four 1.4GHz cores vs. two 800MHz cores in the Apple A5.
When it comes to the GPU, the S3 uses the Mali-400/MP4, which thoroughly outclasses the PowerVR SGX543MP2 in the A5. Anandtech provided some preliminary results that show how wide the graphics gap is on some benchmarks.
The iPhone 4S is significantly smaller but heavier than the Galaxy S3. The Galaxy S3 has a volume of 83 cubic centimetres (136.6 x 70.6 x 8.6 mm) while the more diminutive iPhone 4S is shorter and narrower, though slightly thicker at 115.2 x 58.6 x 9.3 mm (almost 63 cubic centimetres).
Despite the more compact outer dimensions, the iPhone 4S weighs 140g compared to 133g for the larger Galaxy S3. Far from a drawback, many users have found the iPhone 4S' denser mass to be reassuring, giving the phone a more robust feel. In contrast, some rival handsets boasting of lighter weight risk feeling flimsy by comparison - there seems to be an unspoken relationship between physical size and expected weight in relation to perceived quality.
Both can record full HD footage, both have eight megapixel sensors and both have front facing cameras (VGA for the iPhone 4S and two megapixel for the S3). In theory, both handsets have similar photographic capabilities, but we'll be testing them side-by-side soon to evaluate which makes the better pocket camera.
The S3 runs Android 4.0.4 Ice Cream Sandwich while the iPhone 4S runs iOS 5.1.1, two distinct and different mobile platforms altogether.
While Ice Cream Sandwich is the best Android outing yet, the Galaxy S3 runs a customised version of the OS, just like every Android phone without a Nexus moniker. The problem with customised versions of Android is that updates can take an age to appear - the Galaxy S2 has only recently seen an upgrade to ICS, for example.
Because the iPhone is the only phone that runs iOS, there are no different flavours on different handsets. When a new version appears, you can install it to your phone straight away with no fuss, and no need for network operators to roll out a specific build. And when it comes to app support, iOS is still leagues ahead of anything else, including Android.
The iPhone 4S sports a 1432mAh battery with an estimated talk time of 480 minutes on 3G. The S3 has a far larger battery capacity at 2100mAh, which translates to a slightly higher talk time of 620 minutes. Samsung needed to equip the S3 with as large a battery as possible, with the large screen and quad-core processor likely to put a real strain on battery life.
Both phones have Bluetooth 4.0, HDMI out (both via adaptors), GPS and Wi-Fi. However, the S3 comes with NFC, GLONASS, Wi-Fi Direct, HDMI out and a microUSB port. An easy win for the S3, assuming, of course, that you actually need or want the extra features.
The entry level versions of both handsets cost around £499 SIM-free/unlocked. However, when it comes to contract purchases, you're likely to find more generous deals on the S3, despite it being a brand new offering. As always with cheap contracts, though, take a very close look at what you're getting for your money. After all, there's no point stumping up for a high-end smartphone and then finding that your package doesn't include enough data to make use of it!