The DD Jammer (not the ball bearing... ) is basically a sleeve bearing HX-40. They do sound frickin sweet... one of the loudest turbos I've heard.
The PS66 is a S300 variant.
I believe there were a few guys making in the low 500's hp with the DD Jammer.
The PS66 probably is a much stronger turbo, though. And will support much more HP.
I guess it all comes down to whatcha wanna do with it.
--Jeff