24 volt input to the controller will reduce the voltage loss a tiny amount. Probably not worth the hour or so to make the wiring changes. In most cases, the 24 volt input will put in about 0.3 more amps per hour in full sun, not much of a change.
However if one panel is shaded, and only putting out say 2 amps, then this will limit the amps output of both panels. While in the 12 volt mode, one panel can be putting out the full 6 amp rating in full sun, and the panel shaded by a tree can put out 2 amps, thus you will have 8 amps total at 12 volts (96 watts), not 2 amps at 24 volts (48 watts).
So keep it the way it is, you will be better off when parked in partial shade - I think. . ..
Just have fun camping, and enjoy the extra power of the panels!
Fred.