I do the same thing. MS S&T is much faster for me to pick my general routes. Easier to zoom in and out, and to get a general picture of what are possible alternatives. I do use MapSource for the route itself. One reason for that is I have found that with the latest map updates back roads are more reliable in MapSource than S&T. I have DeLorme Topo USA which has some nice features, especially if you are concerned about elevation. It just isn't as easy to get what you want. Kinda complicated.