Nvidia has better drivers by far, and better compatibility with games. I'm using a 7970 right now and absolutely hate the drivers. I regret buying it.

Not to spoil your party, but you might get even more dissappointed getting an Nvidia back.
The one thing I actually was pleased about with my Radeon HD 6770 was that is allowed me to play a lot more old games with less hassle than with my previous Geforce 9600.
Nvidia hasn't exactly got a good track record for maintaining old game compatibility with each driver update.

Maybe that's the case with old games, Nvidia has better compatibility with new games though. I don't remember having issues with my 8800GTX, but that's an older card so it's probably not fair for me to use that as a comparison.

For some reason I always got the picture that in general Nvidia has been having better GPUs than AMD every since their huge failure series, 5xxx. I don't think drivers can be compared that easily, what you should be looking for is the one with least amount of specific brand issues.

I switched multiple times between NVidia and ATI cards over the years, and from my personal experience I have always found the NVidia drivers to be better, more stable, less clunky UI (personal preference), even thought ATI made huge progress between their first drivers of years ago which were barely usable and the current ones.

EDIT: But both are usable so nowadays I wouldn't really consider drivers as a major criteria for the choice of a new graphic card.

I haven't got any first-hand experiences of AMD, but my GTX 560 Ti OC has worked just fine, drivers and all, for the three-ish years that I've owned it.

I've jumped between both brands, and they both get the job done.

I've been using ATI/AMD for a while, and the only time I actually had a serious issue was when, in the rather distant past, I decided to run a popular and often hyped 3rd party driver cleaner. Hosed my driver install and forced me to re-install the OS to sort it. A good lesson learned. Since then, I've avoided such programs, simply uninstalled and updated drivers in the "normal" way and have had no problems. Sometimes I can't help but wonder how many folks might be creating problems for themselves running those sort of programs unless they truly need to for troubleshooting a highly specific issue.

Beyond that, I think the only other issue I had was when I let my drivers fall far out of date and tried to run a recently released game. A quick driver update fixed it for me. Again, my own fault and another good lesson learned.

I've had pretty good success with Nvidia too. A couple compatibility issues with very, very old games from time to time when I last used them, but forgivable and generally fixable with some research and tweaking.

I have to say that is a loaded question

I don't have a brilliant card "Nvidia 670 GTX OC" but I cant complain too much about it

If you read the forums, many had issues earlier this year and late last year with Nvidia drivers - just read a few forums in regards to Tomb Raider and Borderlands 2.

The problem appeared to be glitches at certain points in the games and was diagnosed as Nvidia's new dye cut for the GPU and the drivers, as only be turning of Tessellation or another setting made it stable.

I cant comment on the issue for the 7 range of Nvidia cards and I have to say I haven't had the glitch problem under the new drivers

What I can say is Nvidia make a good reference board and the drivers tend to be good. I haven't had a great experience with AMD at all, with faulty cards and driver issues all the way. But like I said that was 2 years + back and I think there fortunes have turned around now.

My opinion is, go with Toms hardware reviews or 3d mark, pick up a 6 series card at bargain price.

I prefer Nvidia

Oooooo and watch your power settings, the PSU is seriously going to aid your stability and high end cards draw a fair few watts of power down the 24V Rail. Get a 700W PSU minimum for high end cards *even when it says 550W will do

I currently have a 1050W PSU, and the rig runs like a dream

Hope all that helps

My issues with drivers is more about older games like the ones from GOG. Who would you say has better driver compatibility for older games?

In that case still go with Nvidia and ignore what I previously said.
Even though AMD seem to have better legacy Direct3D support almost all of these games can also be run with glidewrappers.

Thanks I'm going Nvidia then.