wiltw
Subscriber
I extensively handled all three back in the 90s, and Bronica and Mamiya were similar in handling; the Pentax 645 was too front-heavy with any tele lens mounted, as the grip handle is attached at the very BACK of the body, putting all of the weight (body+lens) and reuslting torque on the right hand, unless you cradled as much weight as possible in the left hand! While it was better engineered for exposure automation (conceptually it was like using a Canon EOS), its lack of interchangeable backs and finders and limited set of leaf shutter lenses (losing any exposure automation in their use) were also considerations.
I struggled with the choice between the Bronica and the Mamiya (the Pentax immediately was dropped from consideration due to the lack of interchangeable film magazines) and ultimately chose the Bronica for its leaf shutter lenses, making it the better camera for use with flash in covering events/weddings, and having a wonderful TTL flash automation as well as separate metering of the ambient exposure automation.
I struggled with the choice between the Bronica and the Mamiya (the Pentax immediately was dropped from consideration due to the lack of interchangeable film magazines) and ultimately chose the Bronica for its leaf shutter lenses, making it the better camera for use with flash in covering events/weddings, and having a wonderful TTL flash automation as well as separate metering of the ambient exposure automation.