In absolute number of dead, it's certainly worse, if only because of the scale of China. According to Henry Louis Gates 12.7 million Africans were abducted by the slave trade. Estimates for the Great Leap Forward are 15 to 55M dead from famine and several million more from violence.

https://www.abhmuseum.org/how-many-africans-were-really-take...

The Great Leap famine that killed between 11.6 - 55 million over fours years, compared to the Atlantic slave trade with estimated deaths from 2 - 60 million (over 200 hundred years).[1]

[1]https://en.wikipedia.org/wiki/List_of_wars_and_anthropogenic...

Go read stories about neighbors eating each others children to survive. It is pointless to compare tragedies as to which is worse, but it is worthwhile to recognize the magnitude of the (unimaginable) suffering caused by bad policy. The point is you wouldn't want to experience either -- neither is a better choice, they were both disasters worthy of keeping in memory.