I must say I'd be very interested in seeing a comparison of the old and new 45's as they are a significantly different design. Shooting them on a crop camera would probably not show much difference.

I have the 45 N and find it quite nice (on a 5d2, not film or M645) but all the Mamiya 645 lenses (except maybe the A lenses) seem to suffer a little from CA wide open.

JJ