In my mind, the ideal hand is one that is balanced, flexible, with a strong arch; also with a broad, toned, supple palm and lean, flexible fingers. However, this 'ideal hand' must be properly connected to the rest of the body and mind to be of any use.
Small hands are not a disadvantage. In fact, hands that are too large are a greater impediment. If you can reach a 9th, you can play just about anything, IMO.
I can reach an 11th and have no advantage over someone with a smaller span. My prof is an amazing pianist, her hands are tiny but she knows how to use them effectively. I think I would be a better pianist if I had smaller hands. Sometimes, large handed pianists run into technical problems that are easily avoided by those with smaller hands. For example, I have trouble playing white keys in between black keys, if my fingers were a bit narrower, this would never be an issue.
Per Sapientiam Felicitas!