It depends upon how much you plan on using it. If only once in a while, a small disposable charcoal unit is easiest to deal with. If using it all time and needed to prepare a LOT of stuff, then something like Weber-Q is good.
If using a gas grill, taping into your camper lines can be a challenge. Not so much tapping into the lines, as much as the pressure regulator differences with the trailer and your gas BBQ. If we were to do it again, we'd do it like we did before, a separate propane tank and small BBQ. That way, you can position the BBQ anywhere. With a hose attached to the camper, you are restricted only the distance equal to the length of the hose. That's not always the best spot to set up a grill.
In the end, both need to be clean up. I think cleaning up a gas grill is more difficult than a charcoal grill. But, if you don't mind black soot touching everything when you pack it way, this it really doesn't matter. Shove it in a black trash bag and stow it away!
HOWEVER, we got tired of both gas and charcoal clean up, and got rid of both. We use an electric griddle now, or over an open fire.
