Can anyone recommend which if these is the better card? Eventually I will have 2 cards but I am starting with one. I have read some reviews and they seem pretty even. On one game one card will perform better than the other and vice versa.
The 6970 has more memory and a faster clock speed but the 580 still beats it in some games. I can't work it out.
Has anyone tested these two cards themselves that can give me advice?
well both are powerful cards, I personally have 2 gtx 580 with a a LCD TV lg 1080P 2.6ms and I can tell you that those togheter are plenty power to play anything at high video settings but after seeing some benchmarks about Watts consumption two 6970 have plenty power for less watts.
2 gtx 580 very very fast but more more power required. die size is 530mm^^2
2 Ati (radeon) hd 6970 very fast and not to much power required for crosffirex due to its die (silicon) size of 380mm^^2
The difference in die size and number in transistors is the reason why one is faster than the other and as a result power watts needed to function. both are great cards with different characteristics Ati radeon has eyefinity up to 5 monitors in a single card nvidia has cuda physx and 2 monitors per card.. If you don't care about power consumption get the nvidia cards if you care get ATI Radeon cards.