LP vs AC

The BTU's of LP AND 120 ac are identical. RV refers will operate the exact same on either source. There is NO WAY to even test to see which way is better. There are way to many variables that would affect an absorbsion cool down rate. Slightly LOW LP pressure and/or a dirty burner will cause slower cooling on LP. Low AC voltage will cause slower cooling on 120(Very common at marginal CG's with AC supply currents). As the OP stated, HE thinks it cools better on AC, NOT LP. But, if so, he needs his refer LP burner and his LP pressure checked. Doug

Ideally.. NO difference, however it is very hard to hit IDEAL when adjusting the burner so there may be some variation can go either way.

Also voltage varies.. Lower voltage gives the advantage to GAS.

My Norcold 1200 operates best on LP.
Whether on LP or Electric, ventilation is the main issue especially in warmer weather. Do you have a fan(s) in the evaporator area.

In testing both methods with our 1992 Norcold 6162 frig with a reman Amish cooling unit there was not much difference.

I've never really noticed a difference between either heat source.

Now if freezer section is Cold (0-10*F) and food section is NOT getting cold enough (below 42*F) then you very well may have a plugged/blocked cooling unit.
Only cure for that is replace cooling unit or new fridge.

Mine also runs best on LP.

Mine runs better on LP over electric. Stays colder and recovers faster from opening the door multiple times especially when it's hot outside.

I use electric to run the air conditioner and that helps too.. ;)

Mitch