It's 1100, so if you're a serf - a servus - you are, in fact, a slave. Roughly 10% of all households listed in Domesday Book (1086) are still slaves, a legacy of the commonality of the phenomenon in Anglo-Saxon England. That William of Malmesbury writes so evocatively about the plight of slaves in Bristol in the 1120s suggests that the halting of the trade was within living memory.

Slavery under pre-Conquest law was a fairly complex phenomenon that could differ surprisingly based on kingdom.and period, but broadly speaking, you would definitely want to not be a slave if the option presented itself. The plight of a slave ploughman is presented in Ælfric's Colloquy:

I do very much more. I have to fill the stable with hay for the oxen, water them and take their dung outside. Alas, I have to endure such hard work since I am not a free man.

A free man (not to be confused with a Freeman or sokeman) would, of course, have been able to hire a day labourer or some boys to help out, and of course would have had the liberty to work at his own rate. Interestingly, Ælfric's slave ploughman still appears to be an included member of the community despite his reduced status. His circumstances are, at least, less severe than those of the slaves witnessed by William of Malmesbury:

They would purchase people from all over England and sell them off to Ireland in the hope of profit; and put up for sale maidservants after toying with them in bed and making them pregnant. You would have groaned to see the files of the wretches of people roped together, young people of both sexes, whose youth and beauty would have aroused the pity of barbarians, being put up for sale every day.

Given the opprobrium that the Normans placed on slavery, it's perhaps not surprising that the Bristol traders quickly reorientated their trade to export to Ireland while they still could as the English market dried up.

In popular culture, however, the term serf is commonly held to apply to peasant tenant farmers as opposed to Freemen or Sokemen who owned their land outright, or post-Conquest, as tenants-in-Chief. The agrarian peasantry was, however, a wide spectrum of social hierarchies. In 1100, the most populous class of tenant farmer were the villeins or villagers, who on average held a virgate of land, a quarter of a "hide" or "ploughland" and very roughly some 30 acres. Broadly speaking this was equal to the land holdings of most Freemen, and as such would have provided a relatively comfortable existence, although of course a Freeman would not have been liable to carry out service rents on his lord's fields. The second most populous class were smallholders and their associate classes of Cottars/cottagers, and borderers, who on average held some 15 acres, but potentially as few as 5, where there was, of course, far less opportunity for surplus.