Now, i have to admit i Любовь both series! I'd say harry potter is unisex and appropriate for all ages, whilst twilight adresses mainly to teenage girls. HP talks about friendship and love, while twilight is еще romantic! Also, hp gives lessons of life, although maybe in some cases, i would prefer Чтение twilight.
Finally, They are both written by two very talented and imaginative writers, j.k rowling and stephenie meyer. They wrote these Книги to give teens (and not only) inspiration and time of happiness. So, if Ты don't like one of these two series, don't blame them! We can't all have the same tastes!