I had both. They are so different in the way they operate and sound that comparison is really hard.
PSR--open the box, plug it in and play.
BK9--open the box, spend two weeks setting things up and then play! Exception is piano and organ. BK9 sounds great there immediately.
I agree Don......the Bk5 was a bit longer to set up also and after that I wasn't that happy & sold it. It sounded ok but the navigation in live play was atrocious.