Good question.  I wasn't really sure about that one. But I voted in a bun, ponytail everyday because my hair doesnt really get caught in much (its short). I think it depends on how long your hair is too, because it can get caught in things more easily. Also It couold depend on weather there is sun damage involved or if it is really cold out.

A bun or braid keeps my hair most tangle free.  The hair at the nape of my neck gets super knotted if I leave it down, unless I'm wearing a top that leaves my back exposed.

My hair isn't braid friendly but I used to bun it nearly all the time.  Low buns but still always the same, usually damp when I did it too which isn't supposed to be good for your hair.  It didn't cause any visible damage or hair loss.  I've never really had a problem with tangles but waist length is the longest I've ever had and that's so long ago that I don't remember if it tangled.

I think much of it will depend on the general condition and hair type you have, length, weather conditions and how you treat your hair under those conditions. 

As long as I don't have any chemical treatments like dyes or perms, my hair can stand pretty much anything but I wouldn't subject my hair to being bunned while wet anymore and I imagine it would affect fx. waist long hair that may be 4+ years old if it was left to blow mercilessly against my back and what not, every day.