In a capturing race, the favorite is the side that has the advantage because of the special features of the type of fight. The criterion for judging who is the favorite depends on the type of fight.
For example, in a fight where one side has an eye and the other side has no eyes, the favorite is the side with the eye. In this type of fight the underdog can win if he has lots of outside liberties.
In a fight where both sides have a big eye of the same size, the favorite is the side with more exclusive liberties. In this case, the favorite is alive. The underdog either lives in seki or dies depending how many liberties he has (exclusive liberties plus inside liberties).