There isn't really a
best GPU brand. It depends on how you're going to use the card.
Are you planning on mining Bitcoins, Litecoins or both?
Are you going to overclock the GPUs?
Are you going to tweak the core voltage?
I personally like the Gigabyte rev. 2 cards. I don't know if it was just bad luck, but my rev. 1 doesn't overlcock as well as the others. The rev. 2 cards overclock very well and the (rather high) core voltage can be lowered to 1.090 V by flashing a F42 BIOS. I use the stock (FX1) BIOS for SHA256 (e.g., Bitcoin) and F42 for scrypt (e.g., Litecoin). Since the card has a dual BIOS, it's painless to switch between the two.
The new versions of the Gigabyte Windforce 3 have hardware voltage lock at 1.250. Also GPU core clock at 1000mhz, stats on the page say 900...
That's outdated information. The rev. 1's stock clock was 900 MHz.