I am a 4.5 player, college tennis coach, and 8.0 mixed doubles player. With all being equal, you put the better player on the ad side of the court. Sometimes due to lefty/righty or a particular weapon or weakness you change, but in general its best to have the better baseliner on the ad side. Most game points are played on the ad side of the court. The better player's forehand is in the middle of the court as well.
Head Men's Tennis Coach @ Yeshiva University. Pro Kennex Ki-5(R) & Gamma RZR 98 (L)
Dunlop Black Widow 17 (63lb) Babolat N.Vy 16 (64lb) USTA 4.5.