Very nice quick overview by
@heavyD, all of which I would agree with.
I would only add: if you can, I would demo all three frames in succession, all with the same string material type if possible (to equalize swing weight from the string bed), and see for yourself. Depending on how recently you played the nBlade, and/or Gravity Pro (you didn't mention which Gravity model), then the Speed MP might feel easy/quick enough to wield, and would probably be the best middle ground between the Blade and Extreme. That said, that you lack too much precision and/or ease-of-maneuverability with the Speed, then falling back to the Blade would probably be the next move. As for the Extreme, while it certainly would offer the highest power-to-weight ratio of the three, as
@heavyD said, control has to come from more swipey mechanics; if you can adjust, great, but if not, then it will probably have to be the Speed or Blade.
Best of luck. Any further questions, feel free.