The only downside, would be the chance of a broken seal between the two panes, and the condensation that can collect between them. That, and a little more expense, and weight.
When creating utopia in a box, the more heat and cold you can keep away from utopia, the better. If you always camp in temps around 75 degrees and 40% humidity, probably not worth the cost. As you move away from the ideal temp, in either direction, then the benefit will make itself known.
I could see the benefit from less condensation on the windows, being huge in cooler temps.
Single pane glass in homes, and condensate is always a problem. Wouldn't be any different in a trailer. In Florida, the codes require a moisture barrier under the windows in homes, because of the desire by some to still use aluminum framed single pane windows. Which IMHO are junk.