I've always liked techno. Not as much as heavy metal or industrial, but it's nice when you want to dance. It's very easy to fall asleep to, work to, or do just about anything to. Paul Oakenfold is in my opinion the best trance artist out there. I like the music that bands play more then lyrics and vocals.
Rap is just to make money.
I dislike both because the singers more often than not do not write their own music. I say music here, not lyrics. The sound of a band is what makes me like them, not the lyrics.