The main advantage is when one player knows the ball is doctored, the other doesn't. When both recognize the cue ball is playing differently both adapt, no advantage.
I bought a fairly early measles ball. Compared to the well worn red circle cue balls we used in tournament play it rolled long. Going around the table it would roll 12-18 inches long. Not enough for a banger to notice but if somebody was playing tight shape they would.
I prefer playing with clean and polished balls. They definitely play differently than dirty balls. One major thing, they play more consistently than dirty balls. I would like to see the balls used in big events cleaned and polished every evening. It would make for more consistent play and minimize the effect of wax or silicone added by a player. I think some are cleaned daily, it should be standard practice.
Hu