QUOTE(DuDe5593 @ Sep 23 2011, 11:13 AM)
Clock speed.
If you wanted to OC, tune up your clock speed.
Then slightly tune up your memory clock.
Be prepared though, you will get BSOD because of instability.
You will need to tune it for few times until you get the right clock.
Yeah lah, the chip itself

you only compare clock speed etc when you have the same model, like GTX 570 and GTX 570.
VRAM is the bandwith, if you going for multi-monitor, then the higher the better.
you judge a GPU by it's model(GTX 560 Ti, GTX 570, GTX 580), not the card's specification, that one later.