With a straight edge you get 100% contact to the snow. One benefit of straight edge out aside from the obvious clip hooking, is side stepping which I like to do when trying to avoid a sketchy kick turn in a tight place. Straight edge out allows you stomp out, or set your effective straight edge first and pull yourself up placing your ineffective side-cut edge in the nook you just created. When traversing icy slopes I like to set my straight edge and use my other ski to kick across the slope kind of like kicking on skateboard. One downside with side cut in, is when you kick a turn your relying completely on your side cut edges. I like what Chris said as well, side-cut in would make initiating pizza style ski turns easier which is pretty much all I know. Anyways next time your out try to take note of how much more confident you are setting the straight edge compared to the side cut edge. Also because you can cut a skin right up to the edge there's not much of a necessity for a metal edge a DIY will work just as good. Take care.