Indentured servitude and slavery were radically different in a lot of critical ways. While some servants were pressed into service, the vast majority of laborers took on the contract voluntarily. Indentured servants who completed their contracts did receive the freedoms and property they were seeking, not in every case, but commonly (and they had legal standing to sue for this and other grievances). The children of indentured servants were not servants, nor were they property in the same sense that slaves were.
Slavery was race based, and it was perpetual. The children of slaves were slaves. They had no rights, legal or otherwise. You could beat, rape, and murder your slaves (not with complete impunity, but with a great deal of leeway). They were literal property, comparable to livestock.
Indentured servitude was grueling, undignified, and often lethal work, but it was in no way comparable to the chattel slavery inflicted on Africans.
/u/sowzer also talked about it in a previous answer