After our first camping season with our 19', which has the 6.7 cu-ft fridge (with 2 drawers below wardrobe), we found the size of the fridge to be more than adequate. We typically travelled with two adults and two nearly grown teens, and spent up to a week at a time without reprovisioning. For us, a smaller fridge would likely have been not quite enough, or would have required either more frequent trips to the store, or greater reliance on non refrigerated foods (or eat out more often). Not having a microwave is no hardship for us.
Dave W - 2013 Escape 19' and 2011 Toyota FJ Cruiser
"When you arrive at a fork in the road, take it." - Yogi Berra