1. Tolerance. My nerves and arthritis let me shoot 9mm regularly. USPSA Minor isn't winning me anything but a Major Flinch wouldn't either and be a lot less fun. Major or full power .45 hurts and will kick me into a flinch in short order. I load .45s way down to keep from retiring the guns. My carry and house guns are mostly 9mm.
2. Recommendations. A lot of people consider .38 Wadcutter to be suitable for self defense.
3. So what about .45 Midrange? Would I be reasonably well armed with a 185 gr at 775 fps? That's about all the fun I can stand for a reasonable practice with the Commander.