But NOTHING in the SLR world can compare to the quality of the modern Rodenstock and Schneider lenses (not to mention you gain the ability to do a flat stitch, add perspective control and/or tilt-swing with a tech camera). These tech camera lenses are designed without a mirror box which allows them to be either fully symmetrical or only modestly retrofocus rather than the severe retrofocus design required when designing around a fixed mirror box size.
+1 with bells on.
I compared a Phase One/Schneider 55mm LS to tech camera lenses of same/ similar length, and the difference was like night and day. no subtle pixel peeping, just worlds apart. Resolution corner and central, color fringing, distortion. completely different levels. As Doug says it is partly the design limitations of having a mirror box as much as anything else. But still - you might need autofocus, a faster aperture, and to be able to see what you are getting through a prism, none of which is possible with Tech cameras. As always YMMV.
As in 35mm digital, you have to note that a new generation of ultra resolution lenses are arriving, designed for highest level digital sensors. It seems they are appearing now for FF35mm and Tech cameras, but not as yet for MF dSLR's. The newest MF lenses from Schneider and Rodenstock for Tech cameras are very very sharp, definitely up with latest backs. The Zeiss 135mm f2 Sonnar that Michael makes such a fuss over here, as "the worlds finest lens", etc, does in fact have a performance not quite as good as the Rodenstock 100mm Digaron-S when both are at f5.6, if I am reading the MTF charts correctly.
And by the way, the P65+ is a wonderful back. Congratulations.