Well, I'd just read a professional review of the M7 vs the Ikon where the reviewer commented how the Ikon's backloading system was an improvement over the M's. I beg to differ. Hence, I started this thread.
I've never used a Canonet nor a Hexar so I don't know how they work. But to me, the M's tulip is far more elegant and effective than the typical manual backloader's slats-on-a-pillar. Just thread the leader to the middle, and you can be sure the spool will take. No worries about the film flying free off the slats as you're busy advancing the darned lever, or the film not turning cos the sprocket holes are not lined up properly with the gear's teeth.
Or, in the case of my electronic Yashica T4, the film not actually feeding through when the mechanism turns after you snap shut the back door. So you then happily snap away until the number reaches 39, and you wonder how come Kodak or Fuji decided to give you so many free frames, and then you open the camera and discover you haven't actually taken a single shot. Cos the film is still sitting unloaded in its canister.
Plus, while the back door is open, it blocks your right hand, so you have to place the camera on your thighs or table in order to use both hands to thread the film. And while loading film hurriedly in the field I'm always worried I might accidentally apply too much pressure on the back door that the hinges break.