Sorry, mis-typed. It's also a PhaseOne body .... so PhaseOne 645 DF body. But PhaseOne and Mamiya (the companies) are linked so the bodies and data backs are interchangeable, and I think the P1 bodies are just Mamiya bodies re-branded. But I am using my old film Mamiya 645 lenses with the digital system.... it's complicated....
Just noticed I also had the 634 instead of 645.... sigh. It must have been a good party....
lol - that is

... for so many years, still, so in awe of the 645's. Love the medium format, but my wallet and talent are both too thin to warrant such a fine camera.
As to "why" Canon, I debated for quite a few years between many different brands, models, styles, until after talking with quite a few other shooters and reading forums, magazines, reviews, etc., and then most importantly holding as many in my hands and to my eyes, boggling about with the menus and controls, went with the 50D, which at the time I acquired it was top of line in its format. What is interesting [and sad] is that actually bought it and couple lenses on way to the last St Louis Blues home playoff game few years ago, taking youngest boy child for his first playoff game.
Funny, how years ago, when digitals where first coming out, becoming more popular, the Luddite in me railed against them,,, as I love film, how it captures the images (the science/physics behind it), and having in a B&W darkroom (and colour slides) for years. Now, hate to see how many $$$'s I'd be spending developing all the film shots that digital gives freedom to shoot, edit, delete, view on large monitor, etc. before printing the exact ones you desire. The instant feedback and gratification, ability to store and share images... awesome.