IMHO, the reason Intel are ahead at the moment is because they have been price fixing, and preventing OEM manufacturers from stocking the rivals products in exchange for discounts on their products.
http://news.bbc.co.uk/1/hi/business/8047546.stm
http://arstechnica.com/tech-policy/...-antitrust-fine-violated-its-human-rights.ars
This has caused AMD to fall greatly behind with 11 sucessive quarterly losses. But even after this, they are still producing chips that are, on average, only 5-10% slower than than Intels in real world senarios, but are selling them much cheaper. The end user wouldn't even notice the difference, unless they were an enthusiast.
If it were me, i'd get AMD if you really want performance for your £. If money is no object to you and you are building from scratch, by all means go intel, but think to yourself, will; you really be fully loading all those cores and resources for a reasonable length of time per day? If not, you may find that you could have bought cheaper hardware and still got decent performance.
With no disrespect to anybody here intended, i have seen numerous threads in this forums where people have said they will use their PC for gaming, and the answer has pretty much always been 'i7, OC 4GHz'. This is completely fine if you can afford to replace your entire system pretty much, but i believe that similar performance could be had with some AM3 or even socket 775 solutions.
The real question that should be asked is how long you intend to keep your PC before you upgrade, because in a years 12-18 months time, we'll have 32nm CPUs from intel with 6 cores, and something similar coming from AMD (45nm or less). << i'll try and find my source for this.