Well for gaming, response time is king. Something with a 1 -2 mS GtG, no higher than 5mS, especially if you are into FPS's.
Since you are thinking of going nVidia, and if your budget allows it, I'd look at something with G-Sync, these monitors are just becoming available now. G-Sync is supposed to be a game changer (pardon the pun), making for a very smooth experience.
With the lower response times, come the higher refresh rates, this usually means that it'll be a TN display although there are a few VA variants out there with high refresh rates. So you'll have a slightly reduced color gamut than say a VA or IPS panel. This shouldn't concern you unless you are into desktop publishing or image manipulation, etc.
In most cases...