assimilation is when OTHER stats get changed, so lets say your mag attack stays the same even if the stone succeds, but your critical gets assimilated from 13>>5 out of bad luck even though its a philosophy stone. If you dont care for your crit, it doesnt matter what % stones you use. If you do care i would advice sticking with 10% or 5% philosophy stones.
for example in this pic a challenge (crit) stone was used to change a swords critical value, and due to assimilation another stat was also changed in the process even though it was only a crit stone.
