Gainward and Asus tend to be extra overclockable (Gainward a bit more, Asus tends to have lots of extras though)
The Leadtek fan is very nice, and would lead to a longer lifespan likely, and probably better OCing.
Haven't seen the Visiontek or PNY, but their cards are usually pretty standard.
All in all, you probably can't go wrong.
Note: This is all general knowledge on my part, I've not actualy owned any of these brands. I am going by what I have researched on makers, as well as what I have heard on the boards here regarding previous models.
Trollin' trollin' trollin', keep them doggies postin', my fingers are swollen, Rawhide!