Interesting point. I do choose seats I prefer for a reason. In my case I would never hesitate to swap 3D for 3C... But I am left handed and I do have a bad right ear so if alone usually like to sit on the aisle with my better ear and left elbow facing the aisle and FA, worse ear facing the middle seat. But if flying with my wife, I flip sides so I can hear her next to me (she gets my left elbow as I eat :-)). Nobody would ever think of it. If alone I'd make the swap happily but one seemingly identical seat is preferred and not identical to me.