I’m 5’10” and the 18 definitively looks the best on me. I have friends several inches shorter who look better carrying the 22. Definitely go by what looks good when you have it in your hand rather than trying to match bag size and height! If your instincts say 22, I bet it looks terrific on you. So many factors— body shape, clothing style, other elements that can’t even be pinpointed— go into determining what bag size suits a person best. 
