It really doesn't make any difference if you're falling off In any case, I prefer our stocky 14.2hh-15.2hh Paint mares. They can do anything from a pokey walk to a full gallop, turn on a dime, and go anywhere.
Dumas is right about 15hh and if her were any taller I couldn't get my foot into the stirups!
I prefer a horse that I don't need to use a mounting block for. Mostly because we ride trails. (you don't always have a tree stump or large rock handy) IF we did arena stuff...I wouldn't care how tall the horse was as long as he was a good one!
My boy is 18 hands tall. When we were doing medieval shows part of the show I did a swordfight with another lady where I got pushed off my horse. It took a long time to learn to fall from that height but once I did it wasn't so bad.