My first M camera was the M2, which I still have. My second was a beautiful M3 but since it didn't work with the standard 35mm lens I sold it and bought a brand new M4-P which I still have.
The finder in the M3 was not that much better for me than the finder in the M2 so I had no compunction in letting go the M3.
I like the simplicity of the M2 even compared to the simplicity of the M4-P. To solve the glasses issue I found proper -2 diopters that screw into the finder that allow me to remove my glasses and see the whole frame in both cameras.
If I were obliged for some reason to need to replace my M cameras I would get another M2 without hesitation. Then perhaps a M6 to replace the M4-P.