The R8 might ultimately be more reliable (though it had early electronic problems - probably/hopefully taken care of on any working ones today).
About Zeiss vs. Leica lenses, you really can't go wrong with either.
They sometimes/often have different signatures which are largely a matter of personal taste. Grossly generalising, later Leica lenses might be "technically" better while Zeiss often has a "look" I like better.
Used R lenses aren't as exaggeratedly expensive as legend has it (at least in Europe) if you shop and choose carefully.
Leica lenses *are* heavy (even the later ones), so if that's an issue, go for Zeiss.
I use both... :-) Zeiss belongs to my SLR travel kit (Rolleiflex SLR), while Leica R is my main "home" SLR kit.