yea the buttons/placket is the best thing about it...and there's cool red stitching in various places that gives it some personality.
regarding PS shirt sizing...it varies. Some shirts I'm a med, some I'm a small. In general a small shirt has a 15" neck, 20" across chest, 18.5" across torso, and long sleeves are about a 35. But I have med shirts with the same specs as well. This is for mainline and PS. The London shirts are cut fuller tho there is a slimfit version of London but I don't have any from there.