Square. I have never been a fan. But lately I feel that it can aid composition and framing.( Just like what Pete Riley will say).Take a shot, make sure you chop of his head, or take s shot, and cut off part of the face, and somehow it will look good. Actually, when you do this, you will be drawn more to the eyes and not the whole head. Ok. Will do more head shot with the head chop off. The first photo looks better, the second need to chop off more!