FI.Uno - good all around short, not as much padding as the Mille

FI.Mille - lots of padding in the chamois, good for longer rides, but will feel quite thick until you get used to it. I thought I hated mine at first, and then they became my go-to 60+ mile short. Probably overkill for a quick 20 or 30 miler.

Haven't worn the FI.13