I know that the Radeon out performs the GTX when OC'd by quite a lot, but I will be ordering this card within the next 2 weeks and noticed that the Radeon 7870's have a black screen problem and are known to be DOA out of the box. So should I take a risk with the Radeon or go with the GTX? Another question is, is there a big difference between the HIS and Diamond version of the Radeon 7870 card?
But it doesn't mean the 660 gtx is a invalid option, it has almost the same performance with less power consumption, better drivers and some exclusive features like txaa and physX.
Honestly it's getting tired the 660 gtx vs 7870, the 660 gtx ti vs 7950 or the 670 gtx vs 7970.
Just go with your favorite brand and previous experiences (in my case i'm all for nvidia cause never had troubles with them since way back).
Both cards perform within a few percentage points of each other, it largely depends on what game you are playing. The 7870 CAN be overclocked to the level of a 7950 which is bit better than a 660, also to note the 7870 performs better than a 660 at high res, that being above 1920x1080 though. I hope this helps