[lewispollard]

> I have never come across a Buddhist source saying that some people are inherently more advantaged than others.

That's essentially the entirety of the Buddha's teachings on karma. I haven't the time to look for sources right now, but I'm pretty sure the close disciples of the Buddha - who all had distinct and extraordinary abilities, either feats of memory or meditation - were explained to have those abilities due to intense work in past lives. Indeed, the Buddha himself didn't chance upon his enlightenment - he made a vow to do it thousands or millions of lifetimes prior, and worked towards it life by life until he was able to achieve it.