A significant 'update' resulted in the 'original' Prince Classic changing appearance during the '80s. It was my opinion at the time that Prince sourced some seriously lower supplier/design/construction details for a big push to prestrung mass marketing for the Classic. Same thing happened to the 'Pro' as it became a completely different racket a decade after the decline of the original Pro. In my opinion, neither 'update' was an improvement over the originals.
I wasn't aware of a change in the Mag Pro. For retailers, the 'window of opportunity' for the Mag Pro was fairly short(couple of years?), even though many users of the Mag held on much much longer