I've got the type in the photo posted earlier. I don't notice any difference in fridge performance. Far as I'm concerned, it's just a watt waster. Not much, but why drain battery power if you don't need to or there's no benefit?
BTW, we cram our fridge full when we go camping and keep it full. If I take a beer, soda or water out, I put another from storage back in, rotating my drink stock and always having at least one cold beverage of my choice.
The design of a fridge should make a slight draft inside anyways;
The cooling fins are at the top. Cold air sinks, warm air rises. The warm air hits the cooling fins, chills and sinks, repeat. A draft from bottom to top starts to form.
If the cooling fins were at the bottom of the fridge, there would be stratification inside the fridge.