For a hobbyist, the differences are subtleties.

For a wedding shooter, a camera with leaf shutter lenses is a huge advantage, and only Bronica (among the 645) has every lens with leaf shutter and you get AE with every lens.

The other brands besides Bronica only have a few lenses with leaf shutter, and since AE automation is linked to the focal plane shutter in those cameras, you lose AE when using a leaf shutter lens.