What is the real difference with out saying the 7970 is faster I know that, but how much slower is the 7950 and is the 7970 worth the hundred more?
Here's the best comparison I can think of: the difference between a 7950 and a 7970 is the same as between the 670 and the 680, somewhat minimalistic. I guess you could say the 7970 would be worth the $100 more, but to be honest, if you get a nice 7950 and overclock it (they are GREAT for overclocking), you can get a lot of the performance of a 7970, with the 7950. It's a good value if you don't quite have the money to throw at a 7970, or if you just want to save a couple bucks to be able to spend on other parts.