I guess that I should add that I have loaded Adox CMS 20 into my M6, attached my Zeiss Planar 50 (which I consider an exceptional lens), threaded my viewfinder magnifier into place and shot some very nice photographs off the tripod using a cable release. After developing in the recommended developer I had some excellent negatives with very fine grain. I have enlarged a couple of those negatives to 16x20 and been very impressed with the results.
I have also loaded plain vanilla TMax 100 into my Pentax 645Nii and, using the FA 645 150mm lens, shot some more very nice photographs off of a tripod using a cable release and mirror lockup. After developing in plain old D76 1+1 for 9 1/2 minutes I was very happy with the negatives. I have enlarged them to 16x20 on my poor little Beseler and been blown away by the prints. I have no idea how the acutance of each lens or each film even compares, or how much grain was in each enlargement. What I can tell you from my experience is that the visible sharpness, the depth and the tonality of the medium format TMax negative was miles better than the equivalent image enlarged from the CMS 20 negative. And that really isn't even going big yet. And 6x4.5 really isn't very big on the large format scale either.
I am reminded of something I read in some book and I must apologize to the author for slaughtering his well written analogy.
Downhill with a wind behind me I can make a small motorcycle go almost as fast as a large BMW, Triumph or Harley. But in the end, if what I want is to ride at that speed for long periods of time, the bigger bike is the only way to go. I think the same holds true for cameras. If I do everything perfectly with just the right film, using a special lens, and enlarging on just the right equipment and paper, I may be able to equal a medium format print once in awhile. But if I intend to make a living at it I probably should just use the bigger camera.