Yes, absolutely.
The Mamiya's lenses plus the huge 6x7 negative will blow the Leica away when it comes to image quality. But there are some drawbacks;
Positives
+ image quality
+ AE mode
+ almost silent shutter
Negatives
- bigger and bulkier
- only 10 shots per roll of film
- plasticky build (never had a problem with that personally)
- no fast lenses - ok if you are happy with f/4
- limited range of lenses (but again, not a problem, how many lenses do you REALLY need!?. The 80mm is superb, I could live with just that)
- 120 film processing is more expensive, but if you are doing your own b&w, then not a problem, I find 120 processing easier.
- top shutter speed of 1/500s
I guess it all comes down to what you want to shoot, your shooting style, and if you plan to print big or not.
If you can have both, then you have the best of all worlds.