Looks like the 2.8 is Manual Focus.
About the shutter vibration, do you have that too with the 2.8? Can't you eliminate the vibration with a very sturdy tripod?
Would you be able to tell me the differences in image quality between both?
The vibration issue is related to the focal plane shutter, and as Michael mentions is very hard to deal with. Very fast shutter speeds help (fast enough most of the exposure happens before the curtains finish moving across the film). Sturdy tripods of course help, as does some weight bags over the camera, but even then it's hit and miss. When using this lens I usually shoot 10 or 12 frames to try and get a few sharp ones. Sometimes long exposure times work OK, again hit and miss.
The new 240LS may help, although the timing isn't ideal yet with the DF body. The focal plane shutter doesn't open with mirror lockup, so even in this mode the FP shutter is moving during exposure. I'll probably sell my 300 and move to that lens when it is released - not ideal but I think it could be better.
edit ... LOL ... can't believe I said "film". Guess that sort of dates me
I meant sensor of course.