I’m not a firm believer that rosin makes that big of a difference. There is one fundamental difference though that I have found regarding potency. Standard “boxed” rosin is very flimsy in how it is packed and because of that it is easy for rosin to fall off your bow and become dusty. Other rosins like “Jade Rosin” are much better in that they are very potent, and last a long time. I have had the same block of jade rosin now for 5 years! Regarding differences between light and dark rosin, I don’t think there is much of a difference. Some violinists would disagree with me completely on that topic.