Which would be better, in terms of quality of life: to be a Roman slave or a lower-caste Indian?

It is better to be a Roman Slave. While lower caste indians or "Untouchables" were usually free, they were outcasts from society and were marked as dirty people that must never be touched. The roman slaves, though subjected to harsh labor and possible death, were given the option of freedom if they work for it. Slaves would sometimes be able to become soldiers and work for freedom that way while others might become free due to a sympathetic owner. During the later years of the roman empire, freed male slaves were even allowed to live quietly and vote. Does this answer your Question?