Dunno, but I suspect it has to do with build quality. If you're going to pound something all night, night after night, it had better be well built (and that includes girlfriends). I used to have a PK-5 which I eventually gave away (mainly because of the 13 pedal limit) but in the time I owned it, it never burped once, a testiment, I guess, to Roland build quality.

For the record, Diki, the "7" has 20 pedals (C-G) and a on-board expression pedal. If you plan on using the old B3 trick of tapping on a pedal (usually the A pedal) to get some attack on your left hand bass, forget it, doesn't work very well. Best use is to midi it to a bass program that has the attack, sustain, and release that you want, already built in.

chas