The manga of course.
The anime had a lot of potential, but Bee Train just ruined it. I really liked season 1, but season 2... oh, what happened to you? First of all, I was kind of mad with them switching the worlds around, since Piffle came after the Shura world in the manga, but whatever. But what really made me mad is how they're just rushing through the canon worlds. I expected waaaay more than 3 episodes for Piffle, and more for Shura. *sigh*
The fillers, oh don't get me started. Okay, I loved the one where they were all drawn by Mokona. Best. Filler. EVER. That's Tsubasa on CRACK. However, the fillers this season have been horrible. I didn't really mind the ones last season, but...
The one with the bus. That was a total waste of my life. The majority of the episodes was them sitting on the bus and Bee Train abusing that beautiful song.
The FaixChii episode... oh, don't get me started. Chii's not a human. In Tsubasa, she's an alarm system. In Chobits, she's a persocom. WHY IS SHE A HUMAN NOW?! And what about HIDEKI?!?! Hideki is Chii's one and only! Not Fai! Fai wasn't in Chobits!
Eh, I need to get off to study for a test, but I'm sure everyone else can explain what else I don't like with the anime. ^^