Traveling down the road - I would use the engine battery cause the alternator will charge it - Might need a larger output alterator though
if just sitting in the camper with no engine running but plugged into shore power - House battery because the battery is being charged by the inverter.
I know some one else is going to chime in but this is my opinion
2011 Rockwood Mini Lite 2306 - Matt
2004 Dodge Ram 1500 Qaud Cab 4x4 with 35" tires and 3.92 gears, Dynatech Longtube Headers & Fabtech 6" lift + Superchips with shift Tuning
Nights Camped 2011 (37) - 2012 (16)-2013 (2) -2014 (5) -2015(0)
USMC 91 - 95 - F/A-18 Aviation Ordnance