Greater genetic diversity, compared to asexual reproduction.
If you think about it, this makes sense because in asexual reproduction, an organism reproduces all by itself, and uses its own genome as the blueprint for its' offspring. However with sexual reproduction, two organisms come together, each contributing half the required chromosomes, and the offspring gets 1/2 it's genes from the mother and 1/2 it's genes from the father. Sexual reproduction allows for greater diversity because it doesn't just rely on mutations to add new diversity to the genepool.
