Totally agree with you. I think the ending of the manga is better because the CLAMP team allows a true ending. In anime serie, you think it's possible a second season, all the incidents between Chii, Hideki, Dita and the other (i don't remember the name) ends well, and then they continues their lives with normallity. But it's all, the story can continue with a lot of new adventures, the totally new feelings of Chii. This situation don't happend on the manga. The feeling of the ending is diferent.
For me, this is my opinion.