I have to say that I am so happy with the free version right now. I used RB in conjunction with CCE SP for Gladiator (only thing removed was AC32 audio) and the movie looked great. I didn't think I was going to ever be able to fit a movie like that to DVD-5 and have it look good. As I siad, I'm really happy with RB Free--so what's on the pro version that would motivate me into buying it?
You have more control over what to keep and take out, giving you even more space for an even higher quality back-up. Besides, the software is so great, I was happy to pay $30 to aid in future development.
pro will give you the option to do full back up, movie only, movie and menu only, or movie and menu slideshow extras. it will also give you the option to buid an ISO and even burn automatically with dvd decrypter or imgburn if you so choose. you will also get lifetime updates free.