In my experience in owning and using over the years (Canon Ftb and Ftbn, Original Canonflex, Leica R6, R6.2, R7, Leicaflex original, SL, SL2, Nikon F and F2, Contarex Bullseye, Zeiss Contaflex IV, and Minolta SRT 101 and X700), the award for smoothest and less vibration goes to the Leicaflex series. They're the quietest, by a good measure, of any of the other mechanical cameras, and I seem to be able to shoot them a stop or two slower then the rest. Sharp pictures, hand-held, at 1/15 is the norm. Apparently they have a sophisticated braking system. I don't have much experience with cameras possessing electronic shutters; they do tend to be quieter then a mechanical shutter.