The Callaway rep told me there is less than a yard between the best and the worst golf ball distancewise. He said the spin is a considerable difference though. Said all players should simply play the best ball for their short game they can afford and leave it at that.
Golf Magazine did a robot test about 1.5 years ago with a shitload of balls (about 100 IIRC) and the spread was in the 7yd range with a 95mph swing speed, with the exclusion of the Nike One Platinum. It was WAY shorter than everything else, 17 yards shorter than the longest Nike ball, almost 19 yards shorter than the longest ball in the test (Titlest NXT Extreme.) The vast majority of balls fell within a 4yd spread. With higher or lower swing speeds I don't know if the gaps would remain the same or if they'd change to an equivalent percentage, I guess that depends on what caused the differences in the first place.