The "BEST" Location is the one that will have the most Space-A seats available to your desired destination and the least amount of fellow passengers competing for those seats on the day you attempt to travel. Unfortunately, that's virtually impossible to predict in advance. The "best" route also depends on your Space-A Category as there may be CONUS limitations if you are an unaccompanied dependent. The "best" route "usually" is from a location that has frequent flights to a destination (e.g. BWI or Dover to Germany) however, since it has frequent flights then you will "usually" find lots of folks competing for those seats from that location. One day, the "best" route to Europe may be from BWI to Ramstein and the next day it could be from McGuire to Spangdahlem or Andrews to Ramstein. "Best" may also involve a departure location that has free parking and is easy to return to to pickup your car. You can check the resources available at www.spacea.net/faq/routes to help you decide which is best for you.
What is the "Best" Location to get a flight from "A" to "B"?