Bennies aren't going to do anything to the flavor, because they never get absorbed into the plant.
H2o2, literally breaks down into h2o, and o2, so I don't believe it would affect flavo, in any way.
Bleach, depending on concentration, could change the flavor, if high enough concentration is used, but that high of concentration would probably kill the plants first.
I've used all 3 and never noticed a difference in flavor, and I prefer bleach. Kills all micros, and keeps roots ultra white.