I chose the Primo bib because I wanted something with lots of vents but warmer than just a shell. Some of the reviewers said it kept them warmer than a simple shell. But alas, it is just a shell. I was hoping the inside of the legs would be soft but it's the same fabric on the outside as inside so you need to wear something otherwise it's quite rough against the bare skin. I'm in the minority that just wears shorts under my bib so keep that in mind.
I'm 5' 11' (almost 6') and 190lbs. I bought a medium and it's snug but flexible. (Like a warm hug.) The fabric is stiff, not flowing. My other bib is an older Northface and I'm guessing it's insulated although the "insulation" is merely a soft lining. The Southbutt bib is a very soft and flowing bib; you never feel it. The Primo is definitely felt because it's stiff - which will probably change with time. Because of that, the pockets are all somewhat tight, not baggy (also not lined so back to coarse fabric feel). And that's fine - it's not an issue. I was just accustom to more baggy pockets before. The cargo pockets are on the front of the leg, which I find isn't quite as optimum as the side of the leg but they are probably trying to keep you looking good and this makes you look slimmer.
The water repellency is great, which is primarily why I bought it. The vents work well.
A decent amount of room underneath for a base layer and some old fleece shorts. No issues with the zipper fly when going to the…