I don't know the other two, but I have a Pentax 645N (not the ii). I consider it basically a 35mm on steroids and love it. I can handhold it with the 75mm if necessary, but it has a big enough frame to be nice to work with in the darkroom. I only have two lenses - the 75mm and the 120mm macro - and they're great. The one thing that would occasionally be handy would be to be able to switch film mid-roll without a black bag or darkroom. But I've had it for about 10 years (maybe more?) and I've only wished for that a few times. It really might be my favorite to use of my pile of cameras.
Welcome to APUG! It's a great forum!