I think it has less to do with the breed and more to do with the horse/ponies personality and the treatment said horse/pony receives.
I've worked at a summer camp for the last 3 summers and I've met some horrible camp horses and some amazing ones. The camp I work at has a variety of horse breeds, the horses come from an outfitter who buys all his horses from auctions or breeds them himself.
They have had draft mixes, QHs, POAs, National Show horses (Arab/saddlebred mix), TB's, Appendix QHs, Appaloosas, Quarter ponies and a variety of grades.
Out of the group that I've worked with, the 2 National Show horses seemed the best for the job. They are both a little spooky but nothing that a little desensitization can't fix and they are both quite tolerant of mistakes.
The draft was really too big for most of the kids to handle, he was a great horse, just really big.
The 2 Q ponies are both pretty good. They both are very workman like horses so they don't tolerate mistakes all too well but they were bred by their owner to work cattle so they kinda need that attitude for that.
The QH's were all a little too high strung for camp work. They needed more of a job to do that just pack kids around. There were a few that did well but both of the good ones needed bute everyday to stay sound.
The Appendix QH was great but he was super slow and probably not a good indicator of the breed becuase he was also really old.
The POA was way too smart to be happy in a camp situation. He was always thinking of thigs to do to get attention. They kids loved him but becuase of his brains he had to be a wrangler horse becuase he could come up with scary "tricks".
The appaloosa did well but he was also really old and pretty much a dorky horse.
Out of the grade horses the one that was the best was a pony that looked to be half halflinger. She would kick at any horse that was behind her but she was the best ride for campers and wranglers alike.
I hope this was atleast semi helpful.
I would never wish the life of a camp horse on any horse though. It's a horrible horrible way to live, atleast the camp I was a part of (which had the best horse facilities in my area.) Unless the horses are the most important thing in camp, it won't end well.
Fabio - 13 year old Arabian/Lipizzaner gelding
Hazel - 14 year old Angora goat
Atticus - 4 year old LaMancha/Alpine cross goat
Rest peacefully, Lacey.