I've tried experimenting with the extremes. On my 12-25 road cassette, I notice nothing. On my 11-30 MTB cassette, there's a difference. On my road setup, the tension of the chain kicks in and dictates spacing of the pulley from the large cog when I let out the B-screw. I think they've figured out modern derailleurs well enough at this point that these small adjustments make little difference unless you deliberately try to mess it up or really don't know what you're doing.