naruto has, as any anime, fillers in it. but besides that i like it. one piece is awesome as long they follow the books to make the series. i read the books of one piece and i find it better than the series.
I like one piece more than naruto. Thats probably because I didn't read the books first though. I like one piece because of the crazy adventures that they have and I really like the characters. I feel that with naruto has parts that are pretty slow, but that is probably the filler's fault. overall though, I love how in one piece the characters develop and how they can go to really odd places and fight the oddest enemies.
I just recently started to watch naruto but i'm a long time fan of one piece and every week it's the same image , me waiting eagerly for the next episode to come out and in between watching some naruto , so in my opinion one piece is better , or better yet , different , one piece has something more and i can keep watching one piece for a long time (didn't like thriller bark to be honest) but for naruto i just can't keep watching it very long it's slow for some reason and i don't know why but it's just to slow and stretched up from time to time , one piece has that too sometimes but i doesn't really stops you from watching like naruto does.