I'll play whatever these days, but when I played competitively, I pretty much always played the ad side for 2 main reasons:
1) With a one hand backhand (which I use), it is more difficult (compared to a two-hander) to get the ball cross court away from the net player going inside out on the deuce side, particularly when facing a good kick serve. It's definitely easier on the ad side.
2) One coach I knew for a while in college said that the more steady player should go deuce side to put consistent pressure on the even, particularly 30-30/deuce, scores, with the more aggressive, hit or miss, harder hitting player on the ad side. Consistent pressure on even scores gives you a lot of break point opportunities, and a lot of opportunities gives the ad player more freedom to be aggressive. Not always my style of play, but many of my partners were definitely much more consistent and not as hard of hitters compared to me.
Just to be clear, I'm not saying the above is necessarily the best way to handle choosing sides, but that's the way the coach operated so we went with it.