Both are good, i found AMD is slightly cheaper with a good range,, a few years ago i found their software updates where hard to navigate, but they have fixed that.
I just recently upgraded my card (like 3days ago
) i went from a GTX 285, and now i have a 7950, and im loving it,, everything maxed, easy to do a simple OC with the software, really comes down to money and availabilty,, the good thing with the 7xxx series is when u xfire them u great responces like 100% increase in performance