watson-holmes is the best, because watson has two syllables just like sherlock. Wat son Holmes. Sher lock Holmes. The same can be said for holmes-watson, because John Wat son & Holmes Wat son.
The next level comes in when we include the first names. Sher lock Wat son Holmes is better bc it has the two syllables before Holmes, & the emphasis is SHERlock WATson HOLMEs, whereas holmes-watson is SHERlock HOLMES watSON & it doesn’t sound natural, or SHERlock HOLMES Watson which also sounds weird. SHERlock HOLMES WATson sounds more like “holmes” is his middle name than the first part of the last name. At least the HOLMES WATson is like JOHN WATson
Speaking of: John watson is already JOHN WATson, so HOLMES WATson sounds ok. Until we add his first name: JOHN HOLMES WATson is just too much. JOHN WATson HOLMES & JOHN WATson holmes is so much better. WATson holmes sounds like SHERlock holmes, & HOLMES WATson sounds like JOHN WATson.
So let’s try an experiment. Try saying these. John Sherlock Holmes. Sherlock John Watson. To me, John Sherlock Holmes sounds much more in-flow than Sherlock John Watson. I might even say Sherlock Watson John.
This is why “Watson-Holmes” is superior to “Holmes-Watson”.