I have a Prophet-5 Rev.2 (1978) and a Prophet-10 Rev.4
Both looks great and sounds amazing in their own ways ....
P-5 has tuning issues with temperature fluctuations and OSC drifting in almost organic ways .. Inspiring and annoying
P-10 is more stable (after 5 minutes) and that's much better in long studio sessions when there's no need to press TUNE button and loose your current settings, for example ...
P-5 keybed is "floppy" and trigger at different hights (old J-wires are bent differently, and sometimes they break = no sound )
P-10 keybed is smooth and firm, altough a bit hard to press for aftertouch .... (Wich I don't use much anyway)
P-5 has only 40 memory "slots"
P-10 has 200 (+ 200 factory.)
P-10 has options that the P-5 lacks : Split, Stack mode, Velocity, Aftertouch, Vintage knob (I wish they upgrade it so you can choose "OSC drifting and / OR filter drifting" independently ... )
That said, I'll never sell any of them
Cheers !