What type of riding are you doing? For the hunter ring, you would definitely want a taller horse. Also, as far as your body type, are YOU "all leg" or do you have a very long body? I find a very tall person with a long upper body looks out of place on a horse with a short neck, no matter where your leg sits. If your legs are really long, a horse with a wider barrel will suit you better, even if the horse isn't really tall.
I ride a horse that is "too big" for me; he's at least 16.1 and a tank (percheron/TB) and I'm only 5' tall (but I am a little on the heavy side). I have a hard time wrapping my legs around him... but I've always liked the bigger horses, and I don't show. I always say I'm going to teach my horse to kneel like a camel so I can mount easily