Obviously, all sites posts terrible performance numbers with AMD Radeon hardware with Lost Planet 2 and Hawx 2, which are related to driver issues or crippled Tessellation usage.
http://www.hardocp.com/article/2010/12/14/amd_radeon_hd_6970_6950_video_card_review/9
AMD Radeon HD 6970 vs. Radeon HD 5870
"The next criteria is to see if the Radeon HD 6970 is an upgrade from the Radeon HD 5870. The Radeon HD 5870 is the previous single-GPU champion that AMD offered. The Radeon HD 6970 firmly takes its place, but is it worth the upgrade?
In F1 2010 the Radeon HD 6970 improves upon the Radeon HD 5870 by 34%! In Civ 5 the Radeon HD 6970 improves upon the Radeon HD 5870 by 19% faster performance. This 19% allowed a rather drastic difference in the playable settings, greatly favoring the new Radeon HD 6970. In Metro 2033 there is a 20% performance difference favoring the HD 6970. In BC2 there was a smaller 6% difference. Finally, in Mafia II there was a 20% performance difference.
In many of the games, there were significant gameplay experience differences between the Radeon HD 6970 and Radeon HD 5870. The Radeon HD 6970 is an upgrade to the Radeon HD 5870, but performance will depend on the game. In some cases you could see 30%+ greater performance, in others you may see only a 20% or less difference."
"AMD Radeon HD 6950
If there is a real champion in this evaluation, it is the AMD Radeon HD 6950. AMD has set the MSRP at $299 for the 2GB Radeon HD 6950. 1GB models may even be cheaper. The least expensive GeForce GTX 570 is currently $349. That is a difference of $50. In all of our tests, the new Radeon HD 6950 either matched or beat the GeForce GTX 570.
In F1 2010 there was a 5% difference in performance favoring the Radeon HD 6950. In Civ 5 the performance between the two video cards was dead even. In Metro 2033 is just slightly faster than the GeForce GTX 570. Once again in BC2 the two video cards are neck and neck. In Mafia II once again the video cards are very close.
The GeForce GTX 570 just got some new competition in town, and the competition is winning. For the same performance, you can save $50 and get the AMD Radeon HD 6950."
http://www.anandtech.com/show/4061/amds-radeon-hd-6970-radeon-hd-6950/25
"Meanwhile the Radeon HD 6950 occupies an interesting spot. Above it is the 570/6970, below it are the soon to be discontinued GTX 470 and Radeon HD 5870. These cards were a bit of a spoiler for the GTX 570, and this is once more the case for the 6950. The 6950 is on average 7-10% faster than the 5870 for around 20% more."
What I can say for my opinion, is that the current generation of cards doesn't improve a lot in terms of pure performance numbers, but indeed you can raise some more eye candy with less impact in performance. But in the end, in pure performance numbers, the HD 5970 still the indisputed leader for now until a newer AMD or nVidia dual solution arrives. So in the end, the HD 6950 is closer to the GTX 570 than the HD 6970.