645 is as smaller neg, but this can be a good thing in that you can bring on the grain if you want to. I printed a 20x16 from tri x and yes there is grain but it suits the image. I love my RF645 and passed on the Mamiya for its greater size, far greater cost and too few shots per roll for street stuff. Both are great cameras, but I found the ergonomics and build of the Bronny that much better and more intuitive. I think this is the most important thing. If you intend to do lots of landscapes the bigger 6x7 neg will make a difference however and would be my choice. I have LF for that so the smaller neg suited perfectly.