We fished with a guide on lake of the Ozarks for crappie back in 2009. We casted and counted down to get the right depth. He used hi-vis and recommended it because he said that you missed many bites that you could not feel, that just moved the line and the hi-vis helped you see that bite. Because of the type fishing we were doing, the fish were hittting a falling jig and didn't have time to "stare" at the line as the jig passed by them on the fall. I would guess the hi-vis vs a non-visible line would depend on type of fishing and water color. I have no proof of this, it's just my opinion.