Clayne, you are right on many level. And i might do a mistake. Most of my pictures are landscapes and usually i fly from New Orleans to whatever place in the west i feel like visiting. To me, the 6x7 format fits better my views and a M7 is easier to carry on a hike. Now the Mamiya will probably be a walkaround camera, and i'l try to get a Pentax 6x7 system that can be found for cheap-er.
Anyway, lots of pros and cons... The biggest for me is the backs that can be loaded with color and b&w..

Tarzan, i'll go on LFF find your PM. Thanks a lot!

EDIT: No message from you on LFF