Really, I think you'd be best served going to Roland's site and reading everything you can about the instruments, then find all the reviews you can online and elsewhere. Saturate yourself with hard, cold, nuts and bolts info about patches, expandability, polyphony, all that.
Then go to a music store and spend as long as you need actually playing the two instruments. Fool around with them just in general, then put yourself in an imaginary performance situation and put yourself through some paces (changes presets, playing some pieces you know you'll want to be playing, etc.).
I would, however, also consider the Yamaha P-series.
Good luck.