Doctor v. Nurse: more responsibility and more opportunities for leadership and teaching.
PA vs. physician is harder, but similar imo. There's also more research potential as a physician.
Personally I also like the crazy schedule that physicians have. I've always thrived on a shift work type schedule. PAs don't really get that. Most people go into PA for the lifestyle. Nurses do but they're over worked, underpaid, and underappreciated. Though I also chose physician because I don't want to be limited in the help I can provide over a PA.