Here are my thoughts on Coolers - you can read the full article at Cooler Type and Packing - Rafting Grand Canyon
1) In this case, size matters.
Bigger coolers are more efficient (read: hold ice longer) regardless of brand - this is pure physics. This also assuming that you fill each cooler to the top with ice and cold items.
2) Cooler management makes a difference. This is REALLY important!
If you want cold stuff at day 17 on a summer desert trip you need to:
Have that cooler sealed for the first 2/3 of the trip, probably have it pre-frozen (a local grocery store, meat packer, or ice cream place may help you out), and maybe need to use some dry-ice.
Keep you cooler covered, say with a Paco Pad. The photo of the boat here shows a cooler covered with a blue Paco Pad and a small white insulating cover under the pad.
Try to stay out of the cooler at mid day. Get in/out of the cooler in the shade in the early morning.
3) The expensive coolers seal themselves. The cheap coolers seal up with duct tape or a user installed seal.
4) The cheaper coolers generally have hinges and latches that break somewhat easily and will be replaced by many users. The expensive ones have much stronger hinges and latches.
5) If price is no object the expensive coolers are great. If price matters the cheap coolers may require some TLC, but will work just fine. The expensive coolers don't seem to have superior insulation, just superior construction.
6) There's a very extensive Cooler Test at this page: 
Cheap cooler - $59.87 - Rubbermaid Marine Cooler - 150 qt.: