The only pro I can think of using a trailer versus 4 down is that you can more easily back up a trailer, if you get yourself into trouble requiring a retreat. It's not recommended (although many have done it without problems) that you try to back up a 4 down setup. Stress on the tow bar is the primary issue. They're set up to pull, not push. The front wheels on the towed may tend to cut sharp left/right during backing, and that's also a problem. However, if you can start your towed, and use the power steering to straighten and control it's front wheel aspect, it can be done over short stretches on flat, or downhill, grades. Don't ask me how I know.
