I use 5X7 and might be considered (at least by me) some kind of mountain photographer. All other plusses and minuses aside, the format gives me a bigger negative to work with both in terms of enlarging and cropping. The fact is, when size and weight considerations are important considerations, and shooting positions are frequently restrictive, cropping may be another very necessary option.
My only caveat, based on ultimate availability, is that if color is a consideration at all, you might as well stick with 4X5. I personally don't use a 5X7 for color work at all. I consider it to be a tool for producing fine art monochrome enlargements.