But it really depends on when to use and when not use retopology: If you use the same base mesh for different variations of characters then a low poly base mesh (and no retopology) will save time and might be better to use the same rig and animation set.

Retopology makes only sense if you create something completely new from scratch. And the tool does not matter. You can make it in Modo, 3dcoat or ZBrush. The result matters.

And keep in mind: only klicking here and there will not make you an efficient topology. You still have to care about polygon loops, bridges and other low poly techniques to have an efficient mesh.