I am not sure if there is a preference related to American vs. International style, but I have been taught both ways as well. My personal preference is the side-together with the left foot start (QQ). For some reason, it makes it easier for me to go into a crossover or a fifth position break sequence or even a cross-body lead or Cuban Walk. Couldn't tell you why that is, other than it's a "comfort zone" thing. Good question, though. I have often wondered myself. I want to say Terence or Jonathan addressed this a couple of years ago, but not sure.