They are quite different in terms of system and focusing method.
What do you want it for?
A rangefinder has two notable limitations :
1. parallax error in very close focus; some RF cameras have viewfinders that take care of this, but still not for extreme close-ups
2. limitation of RF system, so longest lenses are limited
RF lenses are ultimately smaller than SLR ones at the same FL, if a small camera is what you need.
If its for collecting, then the good thing about a rangefinder is that it has less mechanical parts compared to a SLR, in case of potential mechanical failure.
The FM2 is more 'renowned' though.