If you want a good finder for still work, you’re much better off with an SLR such as the Nikon F3. The M3 is a stunning camera but it’s usability is very low for anything but some casual stuff. People like them for the prestige.
Same goes for Canon, but there lens compatability for older models is more limited. Added added benefit: The F4 works with G-versionen lenses, if memory works well, and those work great with the z-mount lenses using the adaptor. Additional added benefit: Fujifilm cameras work great with f-mount and an adapter as well.
Invest in lenses, not cameras.