I hate to say this because I just joined the team but I'm having issues with my 7970. It's not stable even at stock settings. Not just with folding but in certain games too. I've tried a bunch of different drivers and still have issues. I'm going to RMA but I have a 7950 coming Friday. I will wait til Friday to send mine off, hopefully the 7950 is as good of a folder as the 7970.
That is unfortunate, hopefully the RMA process goes smoothly for you, good luck!
For folding I doubt there would be much difference between a 7950, and a 7970.