Cooler performance comes down mostly to wall thickness and how well the lid actually seals — differences that are easy to overlook next to a brand's marketing claims about ice retention.
Insulation thickness is the core spec
Thicker insulated walls hold cold longer, in roughly the same way a thicker winter coat holds body heat better than a thin one — this is basic physics, not brand magic. Premium, high-end coolers with genuinely long ice-retention claims (measured in days, not hours) generally have noticeably thicker walls than basic budget coolers, and that thickness is a big part of what's actually being paid for at the high end, beyond just brand name.
Ice-to-content ratio determines real-world performance
Manufacturer ice-retention claims are typically tested with the cooler mostly filled with ice and minimal other content — a cooler packed mostly with food and drinks, with comparatively little ice, will not hold cold nearly as long as the same cooler filled mostly with ice in a manufacturer's test. Packing a genuinely generous amount of ice relative to what's being cooled, and pre-chilling food and drinks before they go in, both meaningfully improve real-world performance beyond the cooler's own design.
Seal quality matters as much as wall thickness
A cooler with excellent wall insulation but a poorly sealing lid loses much of that advantage to warm air leaking in around the edges every time it's opened, or even while closed if the seal isn't tight. Checking how snugly a lid actually closes, and whether it has a real gasket or seal rather than just resting on top, is worth doing in person if possible, since this detail doesn't always show up clearly in photos or spec sheets.
Rotomolded vs. standard construction
Rotomolded coolers are formed as a single, seamless piece of thick plastic, generally offering the best insulation and the most durability against impacts, but at a significantly higher price. Standard injection-molded coolers are lighter and more affordable, with perfectly adequate performance for shorter trips and less demanding use, but generally can't match a rotomolded cooler's ice retention over multiple days.
The one thing people forget
Check the actual usable interior capacity against the cooler's external dimensions, not just the advertised quart or liter rating — thick, well-insulated walls take up real interior space, meaning two coolers with similar exterior sizes but different wall thickness can have meaningfully different usable interior volume.