I currently have M3, M4 and M6 models. I used to have an MP and an M4-P. Never had an M6TTL or an M7. Of all of them I use M6 mostly, but I think I'd have to say the M4 is my sentimental favorite. The M3 I got "just to have one", dumb as that sounds I confess. The lack of 35mm framing (googled lenses and clip-on finders don't do it for me) and the evidence the rangefinder is starting to come unglued are deal-killers for me against traveling with this camera. I got a rigid chrome 50 Cron that lives on the M3 and I use it around town for occasional shooting. The MP IMO was a huge waste of money, the finish got marked up (not the "patina" people dream of) and I had to caulk the viewfinder to keep out dust. Thanks to the huge price jumps, I got all my money back when I sold it, and bought not one but two M6 Classics and a Voitlander 28/1.9 with the proceeds. I only had the M4-P for a year, it had been overhauled by Sherry Krauter just before I got it and yet some shutter speeds were too fast and others too slow, probably only a half a stop but definitely made the camera unsuitable for shooting slides as I do. Otherwise it was a nice camera and had I kept it longer I would've just sent it to DAG to have the shutter timed (he did my M4 and it's spot on for slides). Basically, there is so little difference between the M bodies, aside from the M3 (finder) and M5 that they're all pretty hard to choose apart based on what they can let me do photographically.