I have the regular (non-undershirt) versions of both, but the premium cottons were from last season and supima cotton from this season. The premium cotton is thicker and has more structure, the supima cotton is lighter, softer, and drapes better. Weather differences aside, if you're looking for a trim/cropped look, I'd roll with the premium cotton. Supima if you want a looser fit.
3/4/14 at 8:47pm