So I've gotten into this discussion a few times on reddit, and Ive just been going off my knowledge of the subject, but is there any significant difference of the two timeliness and how slaves of all races were treated?
What two regions are you interested in comparing? There is a lot of variation throughout these two periods in terms of where slaves were held.
Now in general, slaves in the Americas during the 1800s were of African decent and were subject to anti-black racism that prevented them from advancing socially in many cases even when they were freed. Another problem with this type of discrimination was that it extended to their children for generations after slaves were freed. This type of discrimination based solely on race was nonexistent during the Early Middle Ages.
If you want to hear more about working conditions, I would gladly tell you but you would need to be specific about where the slaves were held.