I want to buy some Hasselblad FE lenses for my Sinar m, because I don't need a shutter in the lens with the Sinar m. Therefore I asked Zeiss for a comparison between the Hasselblad Distagon T* 4/50 CFI and the Hasselblad Distagon T* 2,8/50 FE.
Zeiss tested them for me in projection mode and told me that there are no significiant differences in image quality. The Hasselblad Distagon T* 2,8/50 FE additional has floating elements.
When I have one Hasselblad Distagon T* 2,8/50 FE, I will see ...
For a period I was caught up in the "alternative" lens craze for my Contax, buying Russian Tilt Shifts, Pentax and Hasselblad FE lenses, with the various adapters, that do require stop down mode.
Quite honestly the 110FE f/2 lens has essentially the same look in contrast and tone as the Contax/Zeiss lens other than the fast fall off that f2 offers, which negates the need to stop down or at least stop down significantly where it becomes an issue.
At F2 it is pretty especially on tight faces and available light, but still something I rarely use.
At least with the Contax you aren't messing with cables from the lens to the back, though unless you are shooting wide open all the Zeiss lenses to my eyes have a similar look.
The Pentax lenses have a softer curve, which are nice for tight beauty work, but this can be fairly easily emulated within the processing of C-1, V4, lightroom, CS, etc, just by moving the sliders, so even though our lens case has grown to nearly 50 lbs. I very, very rarely use anything but the standard Contax/Zeiss lenses.
In fact for tonality, color, and overall look, (except for focus falloff) I find the various processors offer more optiions than lenses (except for that Russian Tilt Shift).
Going from C1 3.78 to V4, to RD to Lightroom can make as much if not more difference than a change of lens contrast.
Now if your buying new then I would hold off until Phase/Mamiya announces how/if/when the new Mamiya will work with the different lenses. The Phase announcement is vague in this regard, but if the Mamiya will actually take Hasselblad lenses without having to stop down that will take a lot of older lenses and put them back in use.
Once again, be careful of lens obsession because you can wind up with a lens case heavier than your lighting package.