On average, men's bibs will:
1) have a longer inseam measurement (usually 9-10 inches)
2) have longer straps
3) be narrower in the hip relative to the waist accommodation, than you would find in a women's bib.
4) have a men's chamois. This will typically be narrower in the sit bone area, but overall longer front to back, particularly in the front, where the chamois has an extra 2-3 inches to cover the male anatomy.

Hope this helps.