Unless you are burning and dodging during each of the soft and hard exposures, split grade printing is no different than using a single intermediate grade filter.
That's true. It does have one benefit though if you are using filters rather than a colour head in that you only need two of them. The disadvantage is the potential for movement whilst changing filters.
"People who say things won't work are a dime a dozen. People who figure out how to make things work are worth a fortune" - Dave Rat.