What space do you have to work with is important. The reason is if you only have 4' x 8' table you may not be able to fit all you would want to do on there with O Scale. For instance, the FasTrack layout may fit on the a 4' x 8' Table but the town your were wanting to put on the table may not. A smaller gauge might fit better with all the details you may want to add to your layout.