This is what I think.
I know that majority (if not almost all) of the 팬 of Twilight are girls. So girls are looking for romance (which the first 책 of Harry Potter lacks). I think there is some kind of a 사랑 scene in the series. In the first book alone, Romance is so visible. In the first book of Harry Potter, there is little 또는 no romance found (but it will progress in the following books).
Just asking a question: What is Harry potter too short out of romance for Twilight fans?
Just my hypothesis. I still vote for Harry Potter.