From what I understand out of the newer Canon rangefinders, the QL 17 is the one people want, but I am not sure if it is the old one or the newer G-III QL 17. I really don't know if they are better or not compared to the old Canon rangefinders.
I think most of the newer ones have photocells that could wear out and are dependent on batteries that have become obsolete without adapters.
I personally favor purely mechanical cameras with no dependence on batteries, and the lesser the mechanical complexity the better.
That would not rule out features that might bring up the mechanical complexities in various manners. I would want it still to have adjustable shutter speeds and apertures from f2 or better, as well as good coated glass. I also want it to be able to stand up to a lot of use where the shutter will not fail easily or other issues that could effect mechanical performance.
I am currently working at restoring a Canonet 28, while probably a good and simple camera, I have been told recently it has some major limitations, namely the battery setting the shutter speed and the light cell that the meter reads from.
I have been able to get to do some low light snaps in Auto mode so far, as long as I am close enough to the subject and the meter reads.
Is it a camera that would be easy and quick to repair with minimal effort or inexpensive to have someone else fix it, when something fails in the camera?
Is it a unique, or does it have a newer operational innovation that previous cameras did not have?
These are some of the issues I would think of when considering getting an old camera, maybe other members here could point out some more.
I do not know anything about these 2 particular cameras you are looking at, but if they are for the most part mechanical and fit well into some of the issues pointed out above, I myself would go for it.
BTW that Canon P is very nice looking old camera.