Without going into brands, id like to bring up a few things I found important when looking at fridges......
Make sure you look at your potential fridge choices in the flesh, imagine getting things in and out of it, working/opening the catch (and bag if you want one), is it a pain to open and close with one hand ?
I suggest looking at where you intend to mount the fridge in your vehicle, then consider what other gear you need to fit in the same area, take note of where the fridge vents will be, because you cant just stack your other gear over the vents as they need ventilation to work effectively, also, can you get to the fridge controls easy from the intended position in the vehicle ?
Compare the dry weight of the fridges, think if you will ever need to lift your fridge into/out of the back of the car, how much weight can you lift, extend and twist with ?, if you are not built like Arnie (or have suspension lift), this may be quite important, especially if you add the weight of a carton of beer inside the fridge ,starting your trip with a injured back is not preferable.
Personally id never buy a car fridge that does not have a drain plug, believe it or not, some do not have one, in this case the weight of the fridge is even more important as you may have to remove the whole fridge from the car and turn it over to rinse, this can also mean leaving the fridge off for a period before turning back on, meanwhile your stuff is getting warm.