Both Barnacks and Ms seem to be slow to rewind, they require turning a knob, instead of winding a fast crank like the screwmount Canons. Both have cloth shutters, no meters, and deteriorating glass in their rangefinders (unless you mean the more modern Ms). So using either is an exercise in history reenactment. I see no reason to claim one is "better". They both are obsolete...and fun if you like quality equipment at the expense of not having modern, fast, plastic, autoeverything.
I'm shooting a 1930 Leica II, a Tower 5L lever wind, a Canon IVSB, and a Canon P. I interchange them all depending on my mood. If I wanted to take a serious, commercial photography gig, I'd be shooting something made in the past 10 years. Probably. But for enjoying photography, give me antiques.