I'm not sure why you say you can't do your own test.... You could use your other camera for exposure, and while 50mm lens won't cover the entire 6x6 negative, you can still print middle of the frame. I think, for testing purpose, it will be sufficient. You might want to do that to test your new purchases.
I only have M645 but the quality of image is far superior than ones from my 35mm counterpart. I'd expect your result to be similar.
I've been using Tmax films. Because it's so fine grained, sharpness and grain-less-ness isn't actually what I perceive as advantage of medium format, at least at my usual 8x10 print size. Ease of evaluating negative is one of the major reasons why I like MF.
In general, my experience shows non-photographer friends are largely oblivious to all kinds of 'defects,' so I wouldn't worry about them. Question really is.... does it satisfy your needs??