The two rival firms will see their flagship smartphones go head to head once the iPhone 5 arrives on 21 September.
What's coming after the Galaxy S3: Samsung Galaxy S4 release date, specs and rumours

Before we get any further, this article will look at the specifications of the Galaxy S3 compared to that of the iPhone 5 so you can see what the differences are. We won't be deciding on a winner.
Take a look at the following two articles for more details on each handset.
Samsung Galaxy S3 review
Apple launches iPhone 5
Samsung Galaxy S3 vs Apple iPhone 5: Dimensions

The Galaxy S3 measures in at 71 x 137 x 8.6mm and 133g. The iPhone 4S, is thicker and heavier than the Galaxy S3 but Apple has outdone Samsung with the iPhone 5.
The iPhone 5 is 59 x 124 x 7.6mm and 112g, according to Apple.
See also: Group test: What's the best smartphone?
Samsung Galaxy S3 vs Apple iPhone 5: Screen

The Galaxy S3 has a 4.8-inch display and while every single iPhone in the past has had a comparatively tiny 3.5-inch one, the iPhone 5 has a 4in display.
Apple has increased the screen size and also the resolution to 640 x 1136, retaining the Retina quality pixel density of 326ppi. Samsung's Galaxy S3 has a slightly lower but respectable pixel density of 306ppi from its 720 x 1280 resolution.

Samsung Galaxy S3 vs Apple iPhone 5: Processor

Samsung uses its own Exynos 4 Quad chip for the Galaxy S3 which is unsurprisingly quad-core. It's clocked at 1.4GHz and is based on the ARM Cortex A9 architecture.
As expected the iPhone 5 has an A6 processor which Apple says is twice as fast as the A5 chip found in the iPhone 4S, including graphics performance. Apple hasn't revealed any technical specifications for the A6 so it's hard to compare with the Galaxy S3's. It is believed that the A6 is dual-core.
Samsung Galaxy S3 vs Apple iPhone 5: Storage

Both the Galaxy S3 and the iPhone 5 come with three storage options, 16GB, 32GB and 64GB. Samsung does, however, include a microSD card slot for expansion (up to a further 64GB) which Apple does not.

Samsung Galaxy S3 vs Apple iPhone 5: Cameras

The Galaxy S3 has a rear facing camera rated at 8Mp with the ability to record video in full HD 1080p quality which Apple matches with the iPhone 5's rear iSight camera, although each has different software features.
Both front cameras on the smartphones can record HD video at 30fps but the Galaxy S3's has a slightly higher rating at 1.9Mp compared to 1.2Mp.
Samsung Galaxy S3 vs Apple iPhone 5: Software

Apple’s iPhone runs its own iOS software while Samsung’s Galaxy S3 uses Google’s Android 4.0.4 Ice Cream Sandwich and a TouchWiz overlay.
Samsung will be updating the S3 to the latest version of Android, 4.1 Jelly Bean while Apple's iPhone 5 comes pre-loaded with iOS 6.