Soeren
Member
This differs somewhat. The mileage depends on the previous user. There are a lot of beat up Mamiya 645 Pros, from extensive studiowork. The older AE finders were excellent and mostly deliver the same readings as a hand held light meter. Detachable backs are good for studio work or weddings. Otherwise, the inserts work just fine. The M645 has bulb mode at least. The motor drive for the Pro is slow and noisy, and you can get one for M645 too. A lighter camera is more prone to camera shake.
So, it always depends on what you need the camera for. I much prefer handling a neat and nimble M645 to a bulky, noisy Pro. As they use the same lenses and similar a shutter system, there is nothing in it for image quality.
Yes offcource there are bad samples of either model
I havn't read intensively up on the older 645 system.
Re. camera shake. No it depends more on ergonomics than weight.
Re. Backs vs. Inserts. I have a lot of trouble changing between color and B&W midroll using insert without fogging the film, dont know why

Re. weight. Hmm The M645 is 1580g with prism and crank. The 645 pro puts 1532g on the scale with AE prism and crank and 1933g with the winder.
Re. bulk. 645 Pro is 124x135x170mm Body, Back, lens and AE finder
645 is. 99,3x122,7x166,5mm Body, lens and plain prismfinder so yes it is a bit smaller by aprox 25X15x3,5mm
Best regards