Now, i have to admit i amor 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 mais romantic! Also, hp gives lessons of life, although maybe in some cases, i would prefer leitura twilight.
Finally, They are both written por two very talented and imaginative writers, j.k rowling and stephenie meyer. They wrote these books to give teens (and not only) inspiration and time of happiness. So, if you don't like one of these two series, don't blame them! We can't all have the same tastes!