Sorry, thought you were asking quality of lenses. Now realised you are asking quality/difference of body.
The M series has obvious advantage in having a longer RF base, which translates into better focuing accuracy. So, in theory, you should be able to get a more accurate focus, thus sharper pix.
Viewfinder brightness, I think the Bessa is better. Translates into better pictures? Dono...
If you use highter focal lengths, then the hight VF magnification of the .85 M models will certainly help with framing and focusing accuracy.
The M series also have softer shutter, thus enabling you to take pictures without everybody looking at you.
Lenses? Depends. If you compare a 1950s made Leica lens with a 1999 made Voigtlander/Cosina lens, then the diff is pretty great, especially if you take colour. The VC lens is better.
But if you compare the latest 90s Leica lens with VC lens, then there may not be significant differences to justify the enormous diff in price. Juz my 2cts. If you are brand conscious, by all means go for Leica, if you can fork out the dough for it.
Waileong, do you by any chance, own or had experience using the 50/1.0 Noctilux?