In my limited experience...Sometimes the ability
to carry weight doesn't correspond with their willingness
to carry weight. I worked with a good sized, solid 12hh, big boned well muscled boy.
Very capable of carrying any child we would consider having ride him. But he learned that if he threw a fit with the bigger kids he would never have to carry anything over say 45 lbs. Simply because no one wanted to make him use his body. When not allowed to act up he would easily carry 140lbs plus. The much lighter boned, though about the same height mare would not act up under any weight we asked her to carry. And was never sore or uncomfortable.
I truly don't understand what this thing is people have about shorter horses not being able to carry as much weight (and if somebody can explain it logically, please do tell). My little 13.2hh 3/4 Arab mare can carry a full grown man for well over an hour and not be at all sore or tired with rigorous training. This video is from when he first started training her, before he found a saddle that fits but you get the idea of size.
A (different) 12hh pony I would ride (at about 130lbs) for over an hour in preperation for her to be ridden by the children. Again, no pain, discomfort or even a touch of being tired. (Please excuse her best friends huge head)
should purchase whatever you feel comfortable riding but I tend to think that a well trained, healthy horse of just about any size would be able to carry an individual of your height/weight. So I would encourage you not discount this two-inch-shorter-than-your-ideal horse simply for those two inches without even seeing/trying her! And. Since taller horses are all vogue nowadays due to this strange idea that everyone that's not 5 years old must have a horse taller than 15hh, they seem to be priced accordingly!
I'll keep my short girl. Easier to mount, not as far to fall, easier to tack up/groom.
So many benefits!