trick question--
on one engine. the Tillotson has better transition .
on another one - they modified the little bitty holes in the bore and improved response.
But in most cases I have seen--the right Walbro works just fine
The wrong one does not --------------
do you think you could could add a Stromberg 48 into the questionaire?
Or mebbe an updraft Zenith?
Or a Carterburetor