I tend to go for the 16.2 - 16.3 range in height...when I first started riding, trainers of the time (this was 30+ years ago) indicated that horses over 17 hands, admittedly not all, can have problems with balance as their center of gravity is so high and maybe that has stuck in my mind.
Now, on that note, in looking for another horse I came across two that were 17 and 17.2 respectively. The 17 hand mare was a thoroughbred but she was massive...definitely looked like a quarterhorse in her build. The only thing thoroughbred about her was her height. The other one I looked at was an American Warmblood..I was thinking 17.2...big but OK as he was already showing first level dressage. They brought him out and put him on the crossties. I took one look and said nope...not gonna happen :). Probably wasn't fair as the horse was an absolute sweetheart and a great mover, had a cute jump in a lumbering canter sort of way but his sheer size made it difficult, as the barn manager said, to get him "together" when riding. There was just a LOT of him. I'm 5'6, so 16.2 in my own height and when I looked straight at this horse, I was dead eye level with the middle part of his shoulder...to say it was a strange feeling is an understatement :)
What Ink said though makes sense. Once you get on them they don't feel that much different in height than any others. It is true the difference is in the gait, most notably at the canter, and once you get used to that it isn't any different. My 16.2 has a rolling canter just due to how he moves and it took at least a half dozen or so rides before I could actually sit that canter.
Last edited by tlkng1; 02-15-2012 at 05:46 AM.