Performance gain by baking details into normal map?

I recently got substance painter and when looking at their tutorial I notice they have a high density object from which they bake a normal. They apply that to the low density mesh.
I can definitely see the advantage when doing so in a game engine however I am wondering if it would make sense to do this for animations?
Would it speed up the rendering by using a normal map on a low poly object vs a high poly object or wouldn’t that make much difference while rendering?

In general using a normal map on a lower poly object will always render faster. But with blender it’s not always an either/or situation, for example you can sculpt with multiresolution and bake from different levels. So you might sculpt medium detail on level 3, and then sculpt fine detail on level 5, and bake from 5 to 3, and render with 3. In other words it’s not a black/white high poly to low poly situation.

There’s times when there is virtually no discernable difference between the high poly and the low poly with normal, and there are times when the low poly with a normal map looks terrible.