I think you're splitting hairs when you get into the high end coolers' performance...they're all going to be very similar.

The tests are interesting, but like the two above, is anyone surprised that the smallest coolers tested perform the best? Makes sense, because the testers are putting the same amount of ice in each cooler, but the smaller coolers aren't cooling the same amount of space the larger ones are. No wonder the smaller ones test better as far as ice retention.