I have both Assos and Gore. I find the Gore sizing is way too big. I have the Ozon bibs and Phantom jacket in medium and they are massive on me. In the Assos line I have the FI 13 S5 bibs, Airjack 851 and the intermediate evo. They fit me perfectly and they are a size medium which is what the Assos sizing chart suggests.
The Gore sizing chart actually suggested a large but I went with medium and their stuff is still huge on me. The straps on the Ozon bibs are a good few inches longer than the Assos and the butt is baggy.
The Assos Airjack 851 is a superb fit - it hugs the body so there is no flapping in the wind and I can still wear a base layer under it. The Phantom in a medium size is like a tent. It is far too big. (how can it wick sweat if it's not touching the skin?)

I'm 5' 10"
156lbs
Chest 38-39 inches