I got a KILLER deal on my fridge. It paid me $70.
I took my 3 way propane AC/DC stock(ish I think it was replaced once) fridge out of my Scamp 16 and sold it for $80. I then purchased an old 2 way AC DC Norcold fridge for a whopping $10. I took it all apart and foam filled the thing to make the insulation somewhat decent. The stock fiberglass fill was terrible in these. Works better than new, and has the same sawafuji swing motor compressor that Engel fridges use. It's a linear motor that has no peak startup current unlike rotary motors.
I've run it for a 500 mile trip across two days (no charging from the tug, and solar
panels removed) along with running the furnace
for one night as it was COLD on only a crappy marine "deep cycle" that was donated to me as it was questionable at best. the battery
finally died when I got back home. With my two golf cart 6V batts and solar
panels it runs forever with no thought at all. I've had it running as such for over a year now. Always on the DC setting.
I agree about the AC/DC version. If there is a price difference in favor of the DC only, get that. Use the difference on thicker 12v wires. The way that these fridges work is they run a converter to run an inverter anyway. The compressors run at 40v AC. With my swing motor fridge on AC, its still running through the same internal inverter that works right off of the 12v. It is just feeding it with it's own small converter.
I didn't look into the truck fridge you are speaking of, but that may use a small DC Danfoss compressor. Quite and efficient little units, but rotary.