>>4419930i think all that matters are the lenses the system can use, whichever aspect ratio you think you can compose with better is what you should pursue. that said, i like the 6x6 format, even for landscapes. 645 is nice if you’re on a budget, getting 4 more exposures can be nice.
if you’re hiking, the mamiya 6 is incredibly portable, but the widest you can go is the 50mm lens. I think that’s wide enough though. 645 might present the capability to use wider lenses, like how the contax (much heavier and questionable electronics, but amazing glass) has a 35mm f3.5 lens.