Very minimal.
The ceramic coating will help keep the heat inside the header thus reducing underhood temps and helping exhaust flow..How much? not sure.....
I believe the 4-2-1 is suposed to have a better mid range and the 4-1 is suposed to have a better top-end....
You probably won't see any difference in power being produced by either one, just where the power is being made....
The amount of power also depends on the other mods you have done too.