I lease a 15.2hh Appendix QH mare.
She is used for low level dressage and trail riding, with some low level horse trials in the near future as her fitness and my jumping ability improve.
I've ridden taller horses (16hh QH gelding, 17hh TB gelding) and I don't mind them. But I'm 5'9"/185 lbs and enjoy the ease of being able to get on without needing a mounting block, even when riding with shorter stirrups. It's also a shorter fall.