I have used 223s, shotguns, 22LRs, 17HMRs, and 22 mags for coons over the years of calling them. Over all, I prefer the 22 mag. I have used only CCI 40gr HPs and they have wqorked like a champ. I too though am thinking about testing some 40gr CCI gamepoints. Once in a while, I will get a coyote that gets curious and comes in to check out the ruckus.
At least with my experience of calling while walking slowly, 90% of the coon I shoot are from tree tops. There have been a few "incidents" with charging coons that I wish I had a scatter gun though. I imagine that I looked rather comical running the opposite direction of the coon!. I remedy this though by not hugging the woodline so close. As said before, a ticked off charging coon that is less than 10yds from you is a disturbing sight!!