Actually, a Wolf seems to be better than a Dragonkin. I have a Wolf with 6 Str, and a Dragonkin with 6 Str, both with a basic longsword, and the wolf does more damage. The wolf has Natural Beauty and Grateful (she's the starter slave) and the Dragonkin has Alcohol Intolerance, so they're the same aside from the the racial traits, and the Wolf's boost seems to outweigh the Dragonkin's +2 Str.
P.S. What if you don't have the race as a slave? You can't check what you don't have.