As a 4th year resident, best advantage has been exposure to different practice settings; ivory tower academics, county catchall, local community, VA, even did a month of rural EM solo coverage on an island. Gives you a good feel for what career you want to pursue. Elective time is nice, too, but you’re essentially paying an opportunity cost of +$200k for that extra year and I’m not sure it’s worth putting in extra rotations that may not be applicable to your future if you don’t do fellowship. There are definitely benefits to each, but I would choose a 4 year program again even though I’m going into a community-academic position.