Sapphire are well known for their "limited" functionality of their pcb's (in other words it will wear down faster than your warranty says, altough u are covered here) and Gigabyte are providing poor quality components on their pcb as well and their cooling system is a joke (shitforce), so between these 2, i would pick the lesser evil if u really want one of these.
Sapphire is well known for being a very close board partner with AMD, creating very good custom products, and their high end like the Toxic and VaporX are extremely well done.
I also know my experience with their warranty department was, quite frankly, outstanding. And it certainly wasn't their "limited" PCB "wearing out." Neither of which would have anything to do with the other. Or is true. That's a load of malarkey if I ever heard one.
This involved a cat, a side fan, and a cup of tea. I fully expected a bill for repair or a regular 6950. Instead they had a brand new 6950 toxic in my hands in 2 weeks, which was a very limited card and out of production over a year.