I just went through a re-do of my boat''s refrig and freezer. For a 12V unit, I would be cautious about "uses the same electricity as a light bulb". There are basic needs for energy to power compressors for refrigeration. Glacier Bay has one of the best technical sections on their web site, and you can estimate your needs, in BTU''s, from that site. Typical for, say, a 5cu ft refrig and 3-4 cu ft freezer, with 4" foam in the refrig and 6" in the freezer is 1800 BTU for the refrig and 3000 for the freezer. This is 4800 total BTU. (Obviously this is just an example--your needs will vary).
The small 12V compressors are virtually all Danfoss, and the daily AH load ranges from 80 to 120, depending on details of lid design, etc. (Again, could be much higher, if insulation or box design is not optimum).
Larger 12V units can do the same job in a shorter time, with higher amp loads, but net out to similar AH daily load. Engine driven units let the main engine provide the power. Both of these drive holding plates that store the cold until the next time the compressors are run--hopefully once a day, or twice a day.
The only unit that may beat the numbers is the newest Glacier Bay unit, which purports to be more efficient than current models, and certainly very powerful. It is described on their web site. I have chatted with them about it, and it seems to be revolutionary. But it is brand new and unproven on boats.
Whatever else, the main determinant of refrig and freezer performance is the quality and thickness of the insulation in the boxes. Good insulation solves a multitude of ills. Poor insulation can kill the best design.
Practical Sailor did a survey of systems a while ago, and most manufacturers were thought of highly by the people using them. Technautics, Sea Frost, Glacier Bay, Adler Barbour, etc.
In my own case, I made my decisions before the newest Glacier Bay unit came out. Also I had plenty of DC power (900 AH battery Bank and multiple charging methods). So I used separate Adler Barbour Danfoss 12V systems for the refrig and freezer, with evaporator plates. I am pleased with the results.