The latter, obviously. The British, being squishy Western types, would never have gotten anywhere near massacring millions.
Both the French and Germans massacred millions contemporaneously, which suggests that Westerners were willing to massacre millions, so long as they have a reason. It seems likely that the British would have done the same if India had sought independence through war, and thus Gandhi's push for nonviolent tactics averted a potentially tremendous loss of human life.
As for the partition, not only is a single million the highest estimate of the death toll, Gandhi was opposed to it, worked to reduce violence during it, and was assassinated in part because of his...
A reminder for everyone: on this day in 1983, Stanislav Petrov saved the world.
It occurs to me this time around that there's an interesting relationship here - 9/26 is forgotten, while 9/11 is remembered. Do something charitable, and not patriotic, sometime today.