It depends a lot - there were highly valued house slaves (such as Greek tutors, book keepers, chefs etc.) that were treated almost as family and often given free upon the death of their master in Rome. These slaves were often allowed to form families, could be allowed days off and even an allowance.

There were agricultural (cash crop estates, such as wine and oilves) and mining slaves that were more or less worked to their death and then replaced.

English serfs were at times treated badly, but mostly they seem to have served as tenant farmers rather than serfs as we know from Eastern Europe. They owed money (often paid in natural goods) to their Lord for land usage, often combined with corvee labour. Depending on how much corvee labour was owed, the status and position of the serf could increase or decrease.

For example, by the 1600s, a serf owed his Polish-Lithuanian Lord 8 days of corvee labour per week (this meant that the serf had to work all week and someone in his family one day per week). I have no reliable sources right now how much the average English serf owed his Lord, but 3 days pop up on google when I do a quick search.

English peasants were, according ot the doomsday book, 12% freeholders, 35% serfs or villeins, 30% cotters and bordars, and 9% slaves.

All English peasants did have legal rights (even if the serfs and cotters were subject to the judiciary rights of their Lord), right to marry whomever they wanted, right to private property, right to inheritance (in England, the tenancy was inherited by the son of the serf/tenant) and right to buy and sell goods on their own.

So, if you were a highly valued houseslave in Rome, you would probably be better off than a serf or a cotter in England. But being anything else in Rome would probably make your life and the prospect of having a family much, much worse than any peasant position in 12th century England.