We have done several direct comparisons between a Double Double and a corresponding system using splitters and in each case the Double Double configuration simply smoked/obliterated/crushed the splitter option in every way possible ( like it weren’t even remotely close eh ).
But the one big advantage that the splitter system does have is its ability to potentially put a pretty final end to any discussion about whether cables somehow affect the sound of a system. Any "cable hater"/flat earther who could sit through a demo that begins with a single cable test and then goes to a splitter system using the same cable type and not hear a very significant improvement should at that point be encouraged to take up another hobby because they have just pronounced themselves functionally deaf ( sorry but there is really no more polite way to say this ).
And btw, given what Doug has found applying the doubling protocol to balanced cables, this also puts the idea that balanced cables as absolutely ideal and heaven’s gift to signal transfer into a kinda weird perspective. Read, you can’t have the perfect cable, as proponents of balanced claim, and then have that prefect cable produce dramatically better sonic results when doubled. Logically, being significantly better than perfect, puts the original claim of perfection into a very interesting light ( like maybe, uhhh, it weren’t so perfect to start with eh...).
And furthermore, every increase in the quality of the parent cable assembly produces a corresponding increase in sound quality of the Double Double version. So while doubling of conductors changes things significantly, parent cable quality is still the main predictor of end result sound quality.