With the catalyst 12.11 drivers the 7970 performs better. Additionally I already have AC3. And although I am planning on purchasing Borderlands 2 I was also planning on buying the games that come with the 7970. I would have already purchased the 7970 if there was no concern over the reliability.
Well i would choose Sapphire over HIS.
And its just 3% above 670. Not such a big difference.
Also That gigabyte is cooler than His/Sapphire.
So consider that too.