I like her (not necessarily dirty) dance songs like Lollipop and Driving best, but I do like the songs like JUICY and Physical thing and BUT.
My favorite songs are usually her "cute" ones, like show girl or Stay. I know a lot of foreign fans think the cutesy songs suck but thankfully for me the Japanese fans like them.
I can appreciate a good ballad too. Suki de and Anata dake ga are so good!
Honestly, I don't like her rock songs like Work it Out! or Hurry up! or Hashire! I can listen to them, but I find myself not listening to them often or even skipping them. (lol I love how they all have ! so I'm destined to dislike them or something) I wish she'd stop doing them.