We have the original 3 way fridge our trailer came with.
Propane gets it cold fastest and tanks last a long time. We get it cold and switch to 100v when shore power is available. When cold switching works well. The 12v really drains the
battery fast; so we would only use it during travel between sites and pre cool it with propane.
Propane will blow out on the road and the manual says to switch to 12v.
"Newer units are likely more efficient than our 1978 fridge"
P.S. After 3 years of looking found a stove replacement. Drove 8 hours south to get the replacement 4 burner magic chef oven, Slid right in, matched our original 22" unit perfectly. The 1977 stove unit came out of a
boler 1700 and we had it serviced by a local gas pro. The stove top is 20" deep x 22" wide at top and only 16" high and a modern units seem to all be 19" high, they would not fit or not have the look wanted.
"Some times though, functionality is more important than looks"
Hope this is of helps