We’ve taken a look at the features of both phones, put them in the ring and told them only one is coming out alive. Here's how they fared…
iPhone 5 - 12 September unveiling, 21 September available date
Samsung Galaxy S3 - Available now, unveiled May 2012
The iPhone 5 has just been unveiled and, in traditional Apple style, we won't have to wait too long to actually get hold of the thing. You'll be able to pre-order the phone from Friday 14 September and it'll start shipping on 21 September.
The Samsung Galaxy S3 has already been released, of course, and has done extremely well in its short time on this Earth. Back in July we heard that the phone had already broken through the 10 million sales barrier, making it a faster seller than either of its predecessors, the original Galaxy S and the hugely popular Galaxy S2.
iPhone 5 - 7.6mm thick, metal casing, non-removable battery
Samsung Galaxy S3 - 8.6mm thick, plastic casing, removable battery.
Apple has taken aggressive measures to make the iPhone 5 as thin as possible. The rear layer of glass has gone, the phone uses a teeny nano-SIM and the screen technology merges its constituent layers to squish everything down as far as possible. As a result it's just 7.6mm thick, a full millimetre less than the Samsung Galaxy S3 - which is 8.6mm thick.
It's extremely impressive, and Apple has also tweaked the design of the phone to make it feel a bit less severe in the hand, despite being mega-thin. Its edges are slightly bevelled, rather than stepped, so it feels little more… hand-friendly. You still might want to grab a case for the utmost in hand comfort though. Crucially, the new etched aluminium back is much less slippy than previous versions and build quality is exceptional.
Samsung's great white (well, pebble blue and white) hope for 2012 has an all-plastic finish that uses a flimsy, ultra-thin back cover. This is the one part of the phone that has caused the most criticism, as it doesn't make it feel all that much like a device you should be spending good money on, even if in practical terms it's just as tough.
The Samsung Galaxy S3 is also significantly larger than the iPhone 5, thanks to its ginormous 4.8in screen. It's 71mm wide, while the iPhone 5 is around 58mm wide. Our top recommendation is to get hold of a Galaxy S3 before buying if it's on your hit list. Some will find it a bit too big for comfort.
iPhone 5 - new-design Earpod headphones, new Lightning power connector
Samsung Galaxy S3 - microUSB charge cable, Samsung noise isolating IEM earphones, adapter
We don't normally compare the accessories of phones when we give them the head-to-head treatment, but Apple's accessories this time around are of note. The iPhone 5's headphones have been given a completely new design, one you just don't see elsewhere.
The headphones are called Earpods, and they're not the typical iPhone buds of old, or the common noise isolating IEM type either. They're small, made of plastic and are designed to nestle into your ear canals, offering a bit more noise isolation than the earbuds of old.
They're incredibly comfortable and fit securely too, and crucially for fellow train/coach/car/plane passengers, the Earpods leak much less sound to the outside world. They also sound pretty good too. Apple has completely redesigned the sound ports to boost bass and even out mid-range. The result is a surprisingly good listen, with good bass response and a notably wide sound stage.
The power cable of the iPhone 5 is also different, using the new 8-pin socket rather than the 30-pin type that has been in use for years. Apple calls it Lightning, which linguistically fits-in rather nicely with its Thunderbolt computer port. You also get a power adapter for the cable and a SIM removal tool.
Samsung's Galaxy S3 is more ordinary in its approach, though no less useful. It features a microUSB charge cable, a power adapter to plug this cable into and a standard pair of Samsung-branded IEM noise isolating earphones. The latter offer some external noise isolation but aren't actually that great when it comes to sound quality.
iPhone 5 - 4in IPS, 1,136 x 640 resolution
Samsung Galaxy S3 - 4.8in Super AMOLED, 1,280 x 720 resolution
Every generation of iPhone since the original of the species back in 2007 has uses the same size screen - 3.5in. That has all changed with the iPhone 5. It now has a widescreen 4in display of 1,136 x 640 pixels.
It's this change of screen style that will make the iPhone 5 able to offer a larger screen without making the phone any wider. Pixel density is the same as the iPhone 4S too, although the new aspect will make it much better to watch movies on.
Many apps have already been tweaked to support the new longer screen while older ones will just leave bars where the extra pixels now live.
The Samsung Galaxy S3 cares a lot less about how wide it is than the iPhone 5. With a gigantic 4.8in display, the Galaxy will be too wide for some hands - it's a whopping 7.6cm across. Screen pixel density will be comparable to the new iPhone, though, with 720 x 1,280 spread across the display.
Each phone uses quite a different screen tech type. The Samsung Galaxy S3 features a Super AMOLED panel, while the iPhone 5 uses a new take on the IPS technology that has been used in iPads and iPhones for years.
Super AMOLEDs offer superb black response and vivid colours, but IPS screens tend to look a little more natural. In our recent comparison of the Samsung and the HTC One X, we found in favour of the HTC's IPS type. In our so far brief time with the iPhone 5, much the same holds true, though the key point to note is that they're both bloomin' good, it's just the size that should persuade you.
iPhone 5 - 1GB RAM, A6 processor, power TBC
Samsung Galaxy S3 - 1GB RAM, Exynos 4412, Quad-core 1.4GHz
One area where the Samsung Galaxy S3 might beat the next iPhone is its processor's figures. The Samsung Galaxy S3 uses the impressive Exynos 4412 chip, which has four cores and runs at 1.4GHz.
Annoyingly, Apple hasn't revealed in-depth technical information about the CPU. At present, we only know that it is two times faster than the iPhone 4S's chip, which has a dual-core 1GHz CPU and PowerVR SGX543MP2 graphics. Will it be quad-core? Will it offer face-melting speed? You'll have to come back in a while to find out. We'll update this feature as soon as we have the full details.
iPhone 5 - new proprietary 8-pin connector, no microSD, microSIM
Samsung Galaxy S3 - microUSB, microSD, microSIM
Perhaps the most earth-shattering change in the iPhone 5 is that it rejects the 30-pin connector used across iPods, iPads and iPhones in favour of a much-smaller 8-pin model. This is comparable in size to the microUSB standard, although it's not exactly the same as microUSB. Apple is never keen on going with the bog-standard option when it can make its own version.
The problem with changing connector is that the new iPhone will be incompatible with current iPhone docking accessories - not good news if you own something like a B&W Zeppelin. However, Apple does offer a connector that acts as a bridge between the old 30-pin socket and the new 8-pin one.
It's all change, but the iPhone 5 doesn't bring expandable memory to the series - no iPhone to date has offered a memory card slot. You're also mostly tied to iTunes when transferring content like music and pictures to the phone.
The Samsung Galaxy S3 is pretty much the polar opposite in its approach. It lets you use microSD cards and uses the microUSB standard. Handily, it's MHL compliant, too, able to output HD video with surround sound audio to an HDMI port when used with the right cable. Unlike the iPhone, the Samsung doesn't rely on sync software to transfer files directly either - you can drag and drop files when plugged into a computer over USB.
iPhone 5 - 8MP, LED flash
Samsung Galaxy S3 - 8MP, LED flash
Although many elements of the iPhone 5 have been improved hugely over its predecessor, the camera has only been given a slight upgrade. It's still an 8-megapixel sensor, and it still uses a pretty standard LED flash. Its aperture is f/2.4 and it uses a five-element lens. Like the iPhone 4S, the sensor offers backside illumination.
The Samsung Galaxy S3 has an 8-megapixel sensor and reams of features including image stabilisation, touch focus, 1080p video capture and an LED flash. However, its image quality is at best on-par with the iPhone 4S's camera (and outperformed by it in some conditions) and we hope that the iPhone 5 will offer some significant improvements.
The iPhone 5 also offers an impressive looking panorama mode - just tap and pan to automatically create an image. Unlike other similar panorama modes we've seen this one keeps the full size image, giving you up to 28 megapixel images - nice!
iPhone 5 - up to 8 hours talk time
Samsung Galaxy S3 - 2100mAh
In typical Apple style, the exact technical specs of the iPhone 5 battery, in terms of mAh capacity, have not been revealed. Instead, Apple has told us about how long it'll last for in real-world terms. It will handle eight hours of talk time, or a whopping 40 hours of audio.
Also, like previous iPhones you can't swap out the battery on the iPhone 5, so if you're caught short without power you're done for... well, your phone is anyway.
Samsung made a particularly strong effort with the latest Galaxy's battery, outstripping most of its rivals by around 20 per cent. For example, the HTC One X uses an 1800mAh unit and the Sony Xperia S a 1750mAh battery.
We expect the iPhone 5 will match or slightly better the stamina of the iPhone 4S - which in turn suggests that the rumoured 1430mAh figure is bunkum. Unless Apple has really come up with some power management miracles, it needs a larger battery than the iPhone 4S - which has a 1420-1430mAh battery.
More than is often the case, the battle between the iPhone 5 and Samsung Galaxy S3 is the very definition of the case between iOS and Android, between Apple and Google. The Samsung Galaxy S3 is more flexible, with expandable memory and a more malleable OS. However, the metal body of Apple's phone feels a lot more premium, and is a much friendlier design for those with less than giant hands. And with the larger 4in screen, it won't feel quite so tiny next to the Samsung Galaxy S3, either.