I have XFX.. I'd recommend Leadtek based on near universal agreement though... I replaced my heatsink on my card with the Zalman VF-700Cu and it works great now.  Before, I was getting very hot temps.  I bought the XFX because it was on Amazon and at the time, I had a bunch of gift cards for Amazon and it made it a no-brainer.. cheapest out-of-pocket expense, so that's what I got.
And it's just fine, really.. never a problem.. but everyone else likes Leadtek, so there's probably a good reason why!