The 18 CU FT refrigerator is standard with an inverter, this is what we have in our 34RL. The gas/electric refrigerator is a $2,000+ option is this really worth it? I think not, so we stayed with the 18 CU FT refrigerator and never have regretted this decision.
We normally tow between 6 and 8 hours a day and the ice cream has never melted when towing. If we where buying again I would get the residential refrigerator, but if you do a lot of boondocking than I would get the gas/electric or a good solar system.
2016 34RL CC; 2008 Ram Mega Cab 2500HD, 6.7L, 68RFE 6 speed, 4X4, Smarty S67