I disagree, I've been using the canon for a year now and with carefull raw conversion and unsharp mask you can get it fairly sharp but you can't get that 3 dimensionality you talk about.
It sounds like you've already made your decision. Go and buy it, and be done with it.
I do not care for the lower rez backs due to viewfinder crop. I shoot Contax, and you cannot afford to cut into the small viewfinder. The Canon viewfinder is larger than the Contax viewfinder, if you can imagine that. Even the P45 crops slightly into the Contax viewfinder; the others crop more.
Take your 35s. Find a dealer. Go and pitch camp at his shop for a half day and TEST THEM SIDE BY SIDE. That is the only way to know. Do not rely on me, or anyone else here, to advise you. It is a very personal choice, and the only way to arrive at an answer FOR YOU is to go and test. And make damn sure to shoot a lot of images when you test, and treat it like a job, then go home, process EVERYTHING, and then compare that factor too. It's the back end of MF that bites you in the ass; the post production. Also, much slower tethering. This list goes on and on. The only way to know is to test, and to test multiple days.