The special virtue of the VIDOM and Imarect (VIOOH) is that the frame edges are in focus, due to the special optical design. This is a key feature of these finders -- they are accurate.
The built-in one on the screwmounts is fuzzy-edged. The zoom ones (Nikon, Tewe, Walz, etc.) are fuzzy-edged.
My Walz zoom finder has some pretty strong diopter at the telephoto end. Not compatible with a 50-year-olds Presbyopia.