Posted: Feb 23, 2018 - 01:21 PM
There are lot's of good manufacturers - Gul, Gill, Ronstan, Stohlquist, to name a few. Sizing depends on the manufacturer (just like with any piece of clothing). I would just reference their fit guide and most online retailers let you exchange at no cost other than shipping if you need to anyway.
My general preference is to err towards the large side both to ensure adequate arm mobility and to allow you to put extra layers on under the smock in cold weather.
sm