I've read both series and while I enjoyed each, I prefer Harry Potter. I found Harry Potter more well written and crafted by far. I enjoy the HP movies, but of course the books are better! The Twilight movies make me want to bang up head against a wall. I'm curious to see what they do with Breaking Dawn though. They're really going to have to tone it down to give it at PG-13 rating.
BTW, my favorite HP book is the Prisoner of Azkaban. :)