long story short, the 9600 uses a newer .13 micron transistor size that makes it better in the long run. The 9500 pro's clock speed is a little bit higher, so it'll get more fps in todays games. The 9600 pro, however, will do better on games in the future because of it's more efficient processor. Plus, the 9600 is quite a bit more overclocker friendly. I would (and have) gone with the 9600 pro.

http://www.hardocp.com/article.html?art=NDU4