A couple here for no tanlines. Back when i was a teen I preferred them... that whole seeing something that is normally covered attitude. Now I think living in your skin is sexier.
My wife prefers none. That way she can wear whatever summer dress or top without it looking uneven.
I grew up on nude beaches and resorts, but when I started going to the beach with my friends I started wearing a bikini thong bottom, so I got a tanline for the first time in my life when I was like 13. I thought it was ever so sexy, because it showed my style of bikini even when I was butt naked :) It still does ;)