In my opinion, videocards with the same amount and type of RAM with the same GPU are commodities. That is, you'll get equal performance out of any one of them. In fact, they all use the exact same drivers, except packaged differently!
So, I'd go with the one that costs the least and looks the nicest. That said, I've had particularly luck with XFX and eVGA in the sense that in the rare event that something does go wrong, they have excellent support.
hows your case for air flow ?
I have xfx 5770 without the the rear venting system 960mhz core clock
doesn't go above 58C when stress testing with the MSI tools
double lifetime says a lot man
mind you I have good airflow
I suggest shopping on newegg instead. You can grab the XFX 5770 XXX edition (factory overclocked) for $175. With XFX you'll get double lifetime warranty and they have the best support in the business. I have that video card, my only complaints is the side of the video card has slots, which vent out most of the heat inside the case instead of outside of the case. Its probably the loudest thing in my system as well.