RB 12's seem to rev higher than most others, from my limited experience. Though overall power is around the Mugen 12's 1.15 horse, 3 port engines of course. Others have said the fit & finish of the RB's internals is better overall.
The Jp's & the MS 12's are sweet, but there seems to be more options now to those slightly modded 12's.
I've seen those newer Picco 12's running well over the last year.