Reddit mentions of Equiano's Travels: The Interesting Narrative of the Life of Olaudah Equiano or Gustavus Vassa the African

Well, to be perfectly honest with you, there's some discourse that corroborates the variation in treatment amongst African slaves. A lot of the headway in discussing this is in fact made by far-leftist historians and social scientists; like in Zinn's "A People's History of the United States". This is what I've read;

I've read that in the earlier days of slavery, looking past the awful conditions of transportation and the staggering attrition rate of the slave passengers, a lot of slaves were fairly reasonably treated. They represented an investment; a form of chattel property for which the slaveowner expected some return (and much of the time they could be employed in non-productive enterprises, such as in houses or as servants to captains and military officers). Indentured servants, by contrast, when they were popular in early America were almost completely expendable. Once their term of service was over they were no longer of any use to someone who made use of their services, and they were often treated like shit. It also helped that many African slaves had prior technical knowledge in practical matters in their home country; such as cultivation of rice and other plants in tropical and sub-tropical climates.

Slaves, early on, were treated somewhat better than indentured servants and were regularly able to secure manumission from slavery. However as time went on and it became more profitable, and especially after England destroyed the slave-trade in 1807, slavery became an increasingly cruel, repressive, and violent practice in America in an effort to extract as much labor as possible from a supply of slaves. Especially when the cotton gin apparently heralded a productive revolution in the cotton industry's slave plantations (I've heard that slavery was becoming unprofitable before this happened?).

Of course, the experience in certain areas, like the West Indies, was always universally bad. Attrition rates to disease meant that they had to provide a maria system of human labor, and they often didn't bat an eye when a slave died. I suppose maybe you didn't mean it in this sense; and perhaps you meant it in the "Confederate Apologist" sense where some people abhorrently argue that "slavery was actually a good thing for the slaves", but I thought I'd point out that the experience of slavery varied considerably over time and space. You should try reading "The Travels of Gustavus Vaasa (Oloudah Equiano)" if you're curious about reading the perspective of one particular slave in the late 18th century who served in basically every region, climate, and historical event imaginable, and became sufficiently educated to learn to navigate ships and write about his experiences.