Hahaha, when I heard everyone going about Yui's songs in the Angel Beats thread, it was a few days before I realized Yui was a character in the series, and not YUI the artist.. xD;;; Then I was disappointed. Her character is cute, but her personality is kind of overbearing. Kills her for me. n n;
Iwasawa was definitely a more cool character, especially as the 'leader' of the band.
Main thing Yui has going for her is that her name-base comes from YUI, an artist i follow. Other than that, i have a small thing against genki characters, so Yui came off as slightly annoying to me. Iwasawa on the other hand, I liked as a "minds her own business" character