Rosa. Rosa's clothes seem to be really interesting design-wise compared to nate's.
For example, the swimsuit like covering on her legs looks more appealing than nate's, with reference to the sugimori art rather than the sprite art. Also, Rosa looks better with the visor, Nate doesn't need one imo since his hair looks like it can stand alone without a cap.
p.s. I've been basing off my OT's from famous artists, and since most new artists are female, it wasn't surprising that I choose Rosa to start b2/w2.