This quote from Steve Anchell in The Variable Contrast Printing Manual , I think, sums up:
Originally Posted by ChristopherCoy
"Split printing cannot create any contrast that the paper cannot produce with proper single filter techniques. What it can do is enable the printer to maintain precise contrtol over the final image by observing and making incremental separate adjustments to the shadows and highlights. As a printing method, it is not inherently better or worse than using a single filter for overall contrast."
That said, I don't prefer the split printing method, I establish the global or overall contrast with one filtration setting, most always the settings on my LPL equivalent to a contrast grade between 2 and 3. I then may proceed to use other filtration settings when burning-in is desired.