For overloads, differential and non-differential types differ in how they trip (release).

Differential is considered to be a higher sensitivity relay as it has phase failure detection. When a difference between two or more of the phases exceeds the Overload relay (OLR) setting it will trip.

Non-differential type is usually more economical. Electrically speaking, if one bi-metallic strip heats up enough to open then the other 2 remaining poles must also heat up enough to trip the OLR. This can extend the time that it takes for the OLR to trip.