AC vs DC refrigerator
There isn't enough information in your post to provide a good recommendation.  However, I can make some recommendations as follows: a) you want to optimize power efficiency, so choose a refrigerator that is just as large as you need  b) the DC refrigerator is indeed a thermoelectric-based system that is extremely inefficient and should be avoided  c) you should be able to find DC, compressor-based (refrigerant) refrigerators - this is a good option  d) also consider a propane refrigerator.