Could someone explain the advantage of split-grade printing to me. I am failing to see how the end result could be much different from using the intermediate filters - though possibly with finer control.

I have an Ilford VC head, which has two light sources. Whe you select a contrast setting the head varies the output to the hard and the soft light. This should be the same as making two separate exposures with one hard and one soft. How is split grade different than this?

With traditional filters I assume the filters effectively do the same thing, but by subtracting light.