This is one of those myths that simply won't seem to die. It is closely related to the "freed slaves were treated worse than slaves" and "sharecropping was as bad as slavery" (I can actually comment on this one since my father's family were sharecroppers when he was a wee lad, NOT as bad as slavery, or serfdom for that matter, not even in the same bloody universe)
Serfs were also able to actually OWN things and make extra cash by working beyond the duties to the landlord (some slave owners would allow slaves with marketable skills like smithing or cobbling to earn their own money, even manage to buy their freedom, most owners, however, took some or nearly all of this extra income, often to prevent a slave managing to buy his way to freedom) sometimes being able to clear the debt that placed them into serfdom to begin with, with others actually have more cash and a better standard of living than freemen in the same area depending on their skills. Serfs were not even the lowest level of laborer, with cottagers (laborers with just enough land provided to feed their family/pay their "rent") ranking below them since a cottager had almost no hope of earning extra income. Then, below the cottager, were the slaves.
Landlords had legal obligations to the serfs tied to his land, this included the fact that thee land they rented was theirs as long as they paid the annual rent and the various "taxes" a Lord would place on them (things like extra eggs or a goose at Christmas or Easter, a "death tax" when the renter died so his family could remain on the land, etc.).
The status of a serf was anything but pleasant, but compared to chattel slavery, where the slave was LITERALLY seen as and bought/sold/traded as if they were cattle or horses, it would be seen as comfortable. No one simply sold your wife or children to get extra cash for the owner. There were consequences, at least on paper, for killing a tenant, slaves were not afforded that sort of protection, beyond a possible civil penalty if you killed the slave of another owner, same as if you killed a horse. Lords did not simply accept regular die offs of serfs as was the case of with many plantation owners in the Deep South, where slaves were worked in weather conditions that were effectively a death sentence (anyone who has been in the Mississippi delta in high summer knows exactly what I mean). The profits generated by this deadly labor were so high that replacements needed beyond the "natural increase" of already owned slaves (I'll wait while everyone digests the implications here...) were insufficient, fresh bodies could be purchased without unduly hurting the bottom line. It was so bad in the Deep South that many SLAVE OWNERS would not allow their slaves to be sold "down the River" (Washington, as an example, prohibited the sale of any slave outside of the borders of Virginia during his lifetime, and made the same provision in his will regarding his slaves who were to be freed at the death of Martha).
I'm going to assume that your post was the result of accepting one of these myths at face value, without having done any independent research, and not slavery apologia. This time.