I bought this is size Medium, though I am usually size small (5'7''/130lbs). The sizes are unisex so even the small would probably not be form fitting, but relaxed fit.
The Medium gives me the oversized look that I want. It is cozy, soft and medium weight, not heavy. I also like the color; it is not the traditional dark navy blue but a nice soft blue color.
I am considering buying another one in Black in Medium; I still prefer the oversized look as it is more on trend. It looks a little more high end, but also good for people who like things simple.