Do you stay warmer in cold water scuba diving wearing under armor under your wet suit or warmer without it?

I am not overly familiar with under armor and their different products, but my inclination is to say without it. Just because a material will add extra warmth when dry using a dead air space does not mean it will when wet. It i probably just more material to trap and hold a little more water next to your body - which you are trying to avoid.