Here'sa synopsis of both:
psr has-
speakers, great sounds, small size & weight, terrific vocal effects, and harmonies.
760 has-
bad sounds, dated styles, large size, BUT a terrific sequencer. It has two mic inputs, but I think the effects are an option - I'm not sure.

I know this is a biased opinion, but "sound wise" there is NO comparrison between the two. GEM has a long way to go before they reach the level of sounds that everyone else already has.