Hot is always the most powerful as far as total package goes. Hot is someone you want to be with sexually. Sexy is also a powerful compliment, but it can be towards someone you find sexy, but not a strong desire to be with. Beautiful is also powerful and shows the guy is paying more attention to you, studying your specific features in more detail. Beautiful shows a bit more respect and a more "gentlemanly" way to express it.
uh they both really mean the same thing only beautiful is more of a mature way of saying the same thing. Sexy or hot is something that generally that guys and sometimes girls kind just rolls of the tongue and is true but more blunt. and can be more just thrown around jokingly.