The most accurate response is:
Each system developed as a way of ensuring labor for colonizers. Each system was based on race, which has had long-term effects on the structure of the societies of the Americas.
This reflects the reality that both chattel slavery and the encomienda system were implemented by European colonizers to exploit labor, often targeting Indigenous populations initially and later African enslaved individuals, leading to significant social and racial hierarchies that have persisted in various forms to this day.