I always wore mens PI mediums. I needed new shorts and tried the men's small then, naturally tried on womens (PI Perls - purple chamois) mediums. I thought they were fine... but the salesperson intervened and had me get smalls.

Much mo better!

When I started cycling I was bigger... and my brain thought (incorrectly) that lycra is stretchy; smaller body it just won't stretch as much.

With cycling shorts I now go into "pantyhose" mode. Fit like a skin...