eh, appearently the rikudou's chakra is strong enough to make any dojutsu stronger to the point where even sharingan w/ rikudou's chakra can outwit someone without the chakra but possess the rinnegan w/ large chakra, so perhaps potency is superior to amount? idk
high potency = high reserves
Indra and Ashura had potent chakra and large chakra reserves but Ashura had the highest amount of chakra while Indra had the strongest chakra quality, one inherited Rikudou chakra while the other had the ability to produce Six Paths Senjutsu, in the end they were both equal.
Another example would be Susano'o where the higher the chakra potency the stronger the avatar is, Sasuke's chakra was potent enough for his Susano'o to destroy meteorites that dwarfed mountains while Naruto would require huge amounts of chakra to reproduce the same feats using TBBs