I wore a few variations of this outfit before I managed to get pictures of it. This tee and black skinny jeans, this look but a different jacket and my beret--and even on this day I couldn't quite make up my mind about the tee; tucked or untucked. Untucked I feel like it has the very modern Parisian chic look. It's the new je ne sais quoi of French style; ease and loose layers, a juxtaposition of classic and edgy elements but nothing skintight. I find Americans (as observed via fashion blogs and street style sites) on the whole prefer fitted clothing; whether it's jeans or dresses there's always this emphasis on the lines of the body being very clear and visible. It goes without saying that the rules aren't hard and fast for every French person or American, but certain elements would definitely be more popular in certain countries.
For myself I almost always define my waist in clothes and I usually define my natural waist. I think it goes back to being petite and wanting to have the look of long legs even if the fact is somewhat different. So I tried my untucked French ease (and almost had a Marilyn moment see the next to last photograph), but inevitably returned to a more fitted look. It's a small detail, but in the end it's all small details that define personal style. Which style (tucked or untucked) do you prefer?