Intel vs AMD: which processor is best?

Buying a computer can be a lengthy process involving many complex decisions, but none come with quite as much associated technical jargon as figuring out the best CPU.
And so before you even know it, you're drowning in talk of cores and clock speeds, socket types and memory controllers, power consumption, caches and more.
While you'll need to consider at least some of these issues, there's an easier way to approach your purchasing problems. And that's to ignore the fine detail, just for the moment, and focus first on a more fundamental question: Intel vs AMD, which processors are the best for you?
You'll probably find that answering this is much more straightforward. And once you've made your choice, many other decisions about your new PC will fall into place, saving you plenty of time.
Intel vs AMD: Intel CPUs
If you're after performance above else (and you've plenty of money) then Intel processors are the way to go. At least, in general - there are several different families available and you need to be careful which you choose.
Intel Core 2 CPUs are still available, for instance, but they've been around for a long time, no longer represent a good deal and unless you're working with an old motherboard, are probably best avoided.
Instead you'll be considering a Core i3, Core i5 or Core i7 processor, which will deliver budget, mid-range or high-end performance, respectively. Except, of course, it's not quite as simple as that, because these CPUs now come in two main flavours.
The mainstream Core i3, i5 and i7 processors are available in a Socket LGA1156 package (this defines how the CPU connects to the rest of your system, and so means you'll need a Socket LGA1156 motherboard as well). This doesn't represent the very latest in Intel technology, but it's relatively reasonably priced, and there are plenty of compatible motherboards around at all price levels.
The latest Core i3/ i5/ i7 processors, code-named Sandy Bridge and available in an LGA1155 package, are rather more interesting. Not only are they up to 40% faster than their predecessors, but they also come with an on-board graphics chip, so if you're not looking for much in the way of video performance then you probably won't have to buy a graphics card.
The CPUs and Socket LGA1175 boards you'll need to run them are more expensive, but only marginally (they're still available on sub-£1,000 PCs) so if you're looking for a good mainstream Intel solution then these are the way to go.
There is a small complication, though. Intel recently identified a problem with the SATA controller in the Sandy Bridge chipset, and had to recall many motherboards. The issue is fixed now, but supplies of some boards may remain short until April, so you might have to shop around.
The other option available right now is to choose a Core i7 CPU in an LGA1366 package. This will allow you to run the very fastest 6-core Core i7 CPUs, which deliver great speeds and are very overclockable. They're also hugely expensive, though, lack extras like on-board graphics chips, and aren't actually that much faster than the high-end Sandy Bridge systems, so we'd recommend you avoid them in most situations.
Intel vs AMD: the AMD competition
AMD processors aren't currently able to compete with Intel for raw speed, but that might be changing soon, and in the meantime they're able to deliver capable performance at an excellent price. And AMD is also far better at backward compatibility than Intel, so there's no confusion over socket types and multiple incompatible versions of the same CPU: buy an AM3 motherboard and it'll run just about anything.
AMD's Athlon II processors, for instance, are the budget products. They're available in X2, X3 and X4 varieties (the number tells you how many cores they have), and in different model numbers according to their clock speed. Performance isn't so great, but Athlon II CPUs will fit in both socket AM2+ and AM3 motherboards, so you'll have plenty of choice when building your PC.
AMD's Phenom II family are their mainstream products, equipped with more cache memory than the Athlon II's, and running at higher clock speeds for better performance. They're available in X2, X4 and even 6-core X6 varieties, and again the CPUs run on both AM2+ and AM3 motherboards.
And AMD plans to release new processors, code-named Bulldozer and Llano, starting this June and July. Many of the CPUs will include on-board graphics chips, some will have 8 cores, and it's rumoured that performance will be 50% up on the Phenom II, which if true would mean they'll deliver speeds very similar to Intel's Sandy Bridge systems.
For the best results you'll need to run to run AMD's next generation CPUs on the upcoming AM3+ chipset motherboards, but the good news is that once again AMD are working to ensure backward compatibility. And so if you buy an AM3 motherboard today, you can equip it with an Athlon II CPU, but still upgrade to a Bulldozer CPU later on, and you shouldn't have too much of a performance penalty.
Intel vs AMD: which is best?
We've looked at the two product ranges, then - but which is best? It all depends on what you're looking for.
If price is key, then the AMD Athlon II X2 255 makes an excellent choice. It's available for under £40 as we write, and has more than enough power to handle basic PC tasks.
If you've a little more money and need extra performance from your CPU, then AMD's best mid-range offering is perhaps the Phenom II X4 965, some 35% faster than the Athlon II X2 255, and yours from around £100.
Intel's LGA1156-based Core i3-560 is a similar performer and available for the same price, though. And the new LGA1155-based Core i3-2100 goes further still, delivering perhaps 10% more speed for under £100, so that would probably be our preferred choice here (depending on your motherboard requirements).
And if performance matters more than anything else, then right now there's no substitute for the LGA1155-based Core i7-2600K (the K means the multiplier is unlocked, allowing the CPU to be overclocked). It's perhaps twice the speed of the AMD Athlon II X2 255, yet is relatively affordable (in Intel terms at least) at around £240.
If you don't have to buy your CPU until the summer, though, it may be worth waiting. AMD's Bulldozer promises performance very similar to the high-end Intel chips, and experience tells us they're likely to be significantly cheaper - so postponing your PC for a month or two could save you a noticeable amount of cash.