While it is all what you feel comfortable be aware that in some competitions if you are riding a large horse then you will look overhorsed which could work against you. While you can have and ride any size horse if you are shorter then generally a smaller horse will be easier both to ride and handle. Throwing a rug over a 14 - 15 hand horse will be much easier that trying to rug a 17 hand one. Saying that if you try hard enough you can make anything work.
If I were you I would get something around 14 - 15 hands high, maybe something reasonably lightly built. Large enough to do lots with, small enough to handle, fits on floats and in stables easy. If I was shorter I would get something like that.
Although if you find a large horse you fall in love with then you can look past height, but remember to be practicle with both small and large horses.
I think it also depends on your leg length. Bc i'm only 5'2 but I have really long legs for my size so I can ride my 18h horses and not look too small bc my legs are long but if I had short legs riding a horse that size i'd look ridiculous. Even all my trainers are impressed by being able to look bigger on a bigger horse bc of my legs. My horse now is almost 16'2h and you guys have seen the pics of us. Everyone thinks i'm about 5'7 or so until I get off lol! So it all depends on how you look on the horse I think.
Here I am in a school group lesson (on the black gelding).
I am 5'5" and he's about 16.3. The girl next to me is 5'7", all leg and on a horse...sorry...drovers pony...around 14.0. The girl next to her (kinda hard to see) is 5'4 and is a fairly good match on a horse around 15.2.