In formal terms, the dominance of the Catholic Church in Latin America mitigated the harshest consequences of slavery. Slaves were allowed to marry, seek protection from harsh treatment by masters, and eventually buy their freedom. In practice, however, very little protection was offered to slaves, either by the Church or the courts. A larger number of slaves were freed in Latin America than in the North, but that was mainly because slave owners wanted to get rid of those slaves who were too old, sick or infirm to work. Death rates among Latin American slaves were considerably higher than in North America, not least because, as well as performing back-breaking toil, they were expected to provide their own food and take care of their sick and elderly. At the same time, however, slave owners in this part of the world were less likely to interfere in the lives of their slaves than their North American counterparts.

There were also significant demographic differences between Latin and North American slaves. Female slaves were much less common in the former, which led to a lower birth rate among slaves in general. Racial mixing, unthinkable in the American South, was more widely tolerated among the Spanish and Portuguese, reflected in a complex legal classification of races. In other words, Latin American colonialists recognized that there were different degrees of blackness and whiteness. But this also had a practical application. Unlike the American South, absentee slave ownership was rife, meaning that slave owners needed a large number of free blacks, mestizos and mulattoes to help them manage their estates.

To me, the major difference between the two is that North American slaves were generally treated better than the ones in Latin America.  This was especially true after the slave trade was banned in 1808.  North American slaves actually increased their numbers by natural increase (rather than by importation).  By contrast, the slaves in Latin America were generally worked to death relatively quickly and did not live long enough to increase their population by reproducing.

Paradoxically, the Latin American colonies were actually less racist towards their slaves.  There were more freed slaves and they were not really treated all that differently than the Indians were (and remember that Indians were a major part of the Latin American societies).  This is very much in contrast to North America where there were relatively few free blacks and the blacks were treated very poorly.

The only major similarity is that slaves in both areas were slaves for life and any offspring they had would be slaves as well.