Neither.
Here's my opinion.
Twilight is a book that's complete and utter rubbish. It's not interesting at all, and the only reason it's popular is that it's surrounded by screaming fangirls going "omg hottie", especially with the movie coming up. It's so boring it basically makes you wanna fall asleep. It's so horribly badly written you just wanna chuck it in the bin. Besides, it's got bestiality in it, since humans love vampires. I'm not trying to be rude, but simply, that's disgusting! The whole concept of Twilight is crap. The book has no good parts whatsoever. As well as that, the writers encourage fanfic, which I detest (please don't bother me for that comment, it's just my opinion.)
Harry Potter WAS good. The first trilogy of books seemed alright, after that, it quickly turned into basically what Twilight is. Boring, romantic rubbish. The ending of the last book was horrible. "Everyone except the main guys dies and voldermort dies and harry marries ginny and ron marries hermione. The End." That was what it was. The whole concept of the books was being cool, not dreadfully boring, wasting whole chapters on Ginny snogging harry.
I gotta say Harry Potter in the end, since it had an okay beginning, but looking at the end of the series, both are as bad as each other.