2015 style has conventional sleeves, as opposed to the raglan sleeves on the 2014 and perhaps cut with a bit more room. The fabric is shinier and a little more lightweight, and doesn't have the cottony-feel of the 2014.
I bought the rusted iron color, not only because I liked it, but because it was priced $10 less than the other colors, which are priced $10 above MSRP. Not sure why the blue and gray colors are priced higher than most anywhere else.
I'm about 5'8" and 175. The medium fits me well and can (barely) layer over a t-shirt. My 2014 size large layers well over anything and has a much looser fit with much longer arms.
Overall, this is a nice piece that has a lot of versatility. Wish they made it in lighter colors.
This review was written in the old system and had content requirements that are different than reviews written today.