It really does boil down to personal preference though - Kazan does have a point that GF cards run
hot. Not saying Radeons are cool - but certainly they have more effective cooling...
...anyway, like I said it's personal taste. If you don't plan on playing tomorrows games - but you insist on performance for todays then ATI is problably the way forward for you. Certainly their mid-range cards also seem a better bet, but some of the older GF cards (like my GF4!) can still hold their own with current software... though that's beginning to change.
At any rate, you pay your money and take your choice - you can't really go wrong with one of the £300 cards - they're
fast. Start compromising with £100 cards and you'll find you have to lower some detail settings... but then you saved yourself £200. See where I'm going with this?
Certainly though if you wait for the next generation of cards to come out, you should see the current lines of cards come down quite significantly in price.... making them much more affordable but not as powerful as the next line... that said the next line are only really needed for the likes of Far Cry, Doom 3, HL2 and so forth... tomorrows games basically.