Considering the prices, it is not much more for an M6 or M6TTL. You gain the 75mm framelines, and metering in the camera. However, in favor of the M4-2 is the simplified viewfinder (compared to the M6) and a slightly shorter shutter release travel. The only importance in the shutter release is that it makes this the fastest Leica rangefinder in shutter release, though in reality they are all so quick that it is nearly impossible to tell any difference. Whether it was Canadian or German made should make no difference, and I state that as someone born and raised in Germany.
Gordon Moat Photography