The short answer
Both are built tough. The difference is what they do and how long they've been doing it. The Milwaukee M18 Jobsite Lunch Warmer (0811-20) is a first-generation food warmer: you pick low, medium, or high, preset your meal time, and it warms pre-cooked food over a fixed two-hour cycle — powered by an M18 tool battery you supply. LunchEAZE is a self-contained hot-lunch system: you pack it in the morning — even with food straight from the freezer — set the exact temperature and the exact time you eat, and it heats your meal completely on its own, with its own included battery, charger, and insulated bag.
Rugged isn't a look — it's a track record. LunchEAZE has been earning one on jobsites since 2019. If you want exact temperature control, meals packed frozen, and the complete kit in one box, the proven pick is LunchEAZE. If you're deep in the M18 ecosystem and just want a reheat riding on a PACKOUT stack, the Milwaukee is a solid tool.