I bought one of these about a month ago. Tried it on first though at a local Evans shop.
I’m 5″11 and 39 chest and quite broad shoulders, the large is a really good fit, pretty much perfect. I didn’t want anything too baggy or tight either. I just use a base layer underneath and once going, even in the recent snow it is great.
Arm pit vents work really well, found it to breathe very well too. I’m really happy with mine. 🙂