That entirely depends, if I'm in the sun all day and I'm all hot and sweaty, I actually prefer unsweetened tea.. it's probably because I can chug it like it's water. If I'm in the mood to relax and watch a movie or something, I'll usually just get the sweetened tea.
I grew up drinking sweet iced tea (my family is from Arkansas), but I can't stomach it now. I drink unsweetened iced tea every day, but I won't drink it from a fast food place. I'm an iced tea snob! lol