Here is my two cents on what I believe the difference to be:
I myself have just started using the Prestige Classic 600 and am enjoying it thoroughly. You said that you were not getting enough power from you "classic" frame. Obviously, it would then behoove you to look for a racquet with more power, despite the arm injuries it may or may not cause in the future. I, on the other hand, find myself bombing shots out of the court with my "weak" prestige classic 600 strung at 56lbs. I have absolutely no reason to switch to a racquet that I can rip because 1) I don't play with huge topspin 2) I would have to use tighter string tension (further stiffening the whole setup) and 3) I can spin my left-handed serve out wide into the net separating two courts 75% of the time. Why would I choose to move anywhere from where I currently am?