tourmania -- nobody can answer your question without knowing what sort of photography you want to do. A camera is just a tool -- you need the right tool for the job -- you wouldn't go to sears and say "sell me a wrench, which is best?" You'd say "I'm rebuilding a Ford and need a set of socket wrenches calibrated in inches."
Nature? An R system camera might work best, especially if you want flowers or close-ups.
Street photography? Either an M or an older Barnack model will do fine.
Travel? I use my Leica CL for this -- compact, built-in meter, massive dependability.
And so on---
So, what do you want it for?