I like structure. I have a bag that's so slouchy it collapses into a puddle when I set it on a counter - honestly it's a little embarrassing! LOL My bag doesn't have to be heavily structured but I do like it to be able to hold it's shape.
Currently I've been gravitating toward slouchy hobos, but I have structured bags in my collection that I love too, like my MJ Stams and Chanel reissue. It kinda depends on my mood and if I want to juxtapose the style of my bag and clothes. I normally dress really casual, so sometimes I like to carry something structured to mix it up.
Oof, I can't choose either, as I have both and love both! I have structured bags for work (yet some of those still have a certain amount of puddling to them, whilst maintaining a distinct shape), and slouchy bags for weekends, and I can't really say that I have a preference for either type. Even my structured bags don't feel boxy or stick out too far underneath my arm, IYKWIM, so they do still hug the body fairly decently. As far as I'm concerned, I really can go either way, as long as I like the style!