I always look at formats in the way that they are like tools...some are better than others. For most work, 6x7 is the "ideal" format. Enough about that. In weddings, modeling, and portraits: squares are great because 1) you don't have to make a detemination on the orientation at shooting time 2) you don't have to adjust your flash on bracket (rotate) because of orientation, 3) you don't have ridiculous devices such as the Bronica "rotating prism", 4) some wedding pictures benefit greatly by "being square" in the album (more foreground...etc), 5) the lens hoods/bellows can be more "optimally" placed: there isn't any wasted "dark space" because you have to adjust for the long side of the frame.
I shot an RB67 Pro-S at weddings, for formals and candids for years. It wasn't bad, but sometimes, having to stop for 2 seconds, rotate the back and recomposing came close to missing the shot.
645 is a good format for lighter, higher speed work. You get more frames, lighter equipment (generally speaking), and the equipment can be smaller & faster (less distance to move hardware around). On my Hassy's, I have a "crop mask" printed from a color laser on transparency with the lines for the equivalent 6x7, 645, and meter patterns printed on it so that I can "prepare" for later cropping. I use this quite often during weddings so that I can shoot quickly and prepare my editing for ease of use. I can keep my camera in one orientation and shoot away.
BTW, ever tried using a WLF on a 645? or any camera without a rotating back with a RECT format? Uh, up is down and ...
I'm not "defending" the square. I'm just point out why the square is more "efficient" in a fast paced production environment. Yes, the auto-metering and lens transfer on the 20x series Hassy's are great, AF can be great in low light or for candids at weddings, having a winder can also be nice. But, one can get just as good as the automation without it.
I started out shooting a C220, so I got used to the square. When I went to the RB's, I had to "relearn" composition for the RECT. Now that I have all square cameras again, I had to "relearn" then square again. Plus, there's just something about having 20x20's framed 24x24 on the wall. They command space like no other.
So there are times when 645 is great, sometimes when 6x6 is great, and sometimes when I want to use a 4x10 Wisner. Just as I feel that there are times when AF or auto-metering is appropriate. Other times, I want the camera to do NOTHING for me and let me "see my own vision".
HeHe, anybody here ever played with a Rolleiflex 3003? That is one camera that makes you want to scream and buy a P&S