Glass wins for the microwave. Stainless wins everything else.

Glass is the right call for reheating at work, but not because glass is better — because stainless steel has no business in a microwave.

Throw stainless in a microwave and you get sparks, a possible fire risk, and damage to the magnetron. Even the rare “microwave-safe” stainless containers don’t heat food well, since the metal reflects the waves instead of letting them through. Glass heats food evenly and is completely microwave-safe, as long as the lid is too — check the bottom of the lid for the microwave symbol.

That said, stainless is better in almost every other way. It’s lighter, basically indestructible, and doesn’t shatter when you drop it in the office kitchen. It keeps cold food cold on the commute and hot food hot if you pack it hot. If your lunch is a salad, a sandwich, or leftovers you’ll eat cold, stainless is the better box.

The real answer: if reheating matters, go glass. If you eat cold, go stainless. And if you want one box for both, get glass — just don’t drop it.