To me, it all comes down to the viewfinder. The earlier knob-wind Canons' with their squinty viewfinders are, to me, too small to easily use. I'm not a big fan of the P, mainly because their viewfinders haven't seem to have aged well these past 50 years (at least on the Ps' that I've handled). My viewfinder on my old L1 was OK, but the camera seemed crude. Leica had it right with the M-series (projected framelines) which Canon wisely adopted with the 7 and 7s. Focusing and viewing with the 7 and 7s is light years better than the P or the earlier knob-wind Canons.
I now use a Leica MP, M3 and a Canon 7. Everything else I sold.