The 50 is a totally sweet lens, specs-wise it tests better than all the others by a small margin. (they are all Great though). I find myself using the 65 a lot as a nice walkaround lens, and it's a good one for that too.
I have some tests from older magazines, where the 7/7II and lenses were reviewed, including a test of all 5 of the lenses at the time (the 210 wasn't out then). They are at
www.edsawyer.com/lenstests/
As for framing with the 50mm finder, I find that the actual film image is usually a little larger than the framelines in the finder, generally. Some people skip the external finder for the 50 and use the fully visible area on the main finder. Personally I tried that, but the external finder shows a bit more than the visible area of the main finder, so a little more accurate for framing.
-Ed
