It’s all relative.
Debbie McDonald is 5’ tall. Petite by anyone’s standard.
Brentina is a large horse. By anyone’s standard.
They were a very successful pair.
Some horses are narrow, some are big barreled and some riders have long legs. Or some a mix of short legs, narrow barrels and so on. A big, tall horse can do the work very well if an athlete and talented.
Period.
I’m a stocky built tall person. 17.3 hands myself (LOL) I fit good on the 17.2 that I lease, but I would be happy to go bigger, If it was a good horse. For me bigger is most often better(not limited to horses)
Personally I like the 15.3-16.1hh range but my mare grew larger then her parents…she finished at 17.3hh…I am just 5’3" so my legs don’t come all the way down her sides…picture a little kid on a fat pony…Here is a picture of me on her… …The savings grace is she is not wide! My 14.3hh pony was much wider then she is…
We bred one that ended up over 18 hands - Steuart was worried about getting him sold because he was so big, but sell him we did. You’d think he’d be clunky and not very adjustable, but actually he was quite nice. He was better over bigger jumps - kinda lazy with his front end when they were low. You can see photos and videos of him here: http://www.dodonfarm.com/muse.html (for reference, Steuart is 6’2").
