i can't quite put my finger on it, but is it because the revelation in pandora hearts is much more grand? with the court and stuff.
i don't like that in naruto it kinda degrades kaguya to the same old 'mother with the child' trope.. sry but i think even if kishi didn't mean to, he's really sexist.
It was just better built up to and overall executed in PH. In Naruto, it came after a ton of questionable events and tons of kittening around. The main thing being him throwing the main villain he's built up for hundreds and hundreds of chapters in the garbage for a character he came up with 10 chapters ago.