Definitely KH 1 for me.
KH1 has a bit more charm to me, the story isn't as confused and the combat feels better to me (tighter), except aerial battles.
KH2 is all around a better game, but the slow start put me off, along with the weird story and combat just seemed to me all over the place, especially those ATE events with triangle (which was a very abused gimmick), and it seemed more repetitive to me as it follows the pattern of Cutscene - fights - more cutscenes - more fights - go to another world - repeat. Also it had way too many battles, worlds did become bigger, but they filled the rooms with more battles, which became tiring to me. Camera was a lot better.