>>55310585Pretty sure bonuses are all additive. So Helping Speed S (7%) + Helping Speed M (14%) = 21% reduction. I believe there's also a cap of 35%.
For a second, I thought since slower pokemon get "more" reduction from the percentage-based reductions, maybe a slower, higher value berry type pokemon could eventually outpace a faster, lower value one. But then I realized that's not how multiplication works.
So in a neutral scenario, although individual berry type values are not linear, they all scale up in proportion to their base values. Couple that with a pokemon's base helping speed, all pokemons' comparative berry output values are pretty much set and their rankings won't change given identical skillsets.