Dry ice is certainly not the way to go, is it? It would freeze anything you put in there, even if you didn't have cans of carbonated beverages exploding...
It is interesting that the block ice and the cubed ice were neck and neck. I prefer block ice (either those plastic blue ice containers or frozen jugs) just because it is less soggy, but I also put stuff like cheese and butter and such in vacuum plastic containers so even if we use cubed ice, they don't get waterlogged.
I think all the coolers would have done better if they hadn't been sitting in the sun on 94°F days...