But comparing species-level selection and individual selection, it makes no sense to say that one is more powerful than the other. They are playing different games.

They are both attempting to influence the same germ line. They are both attempting to influence the same set of traits. It makes reasonably good sense to look at a trait - and to ask whether it is more for the benefit of the individual or the species.

For example, one such trait might be: a love of swimming. That might be bad for an individual (drowning), but good for the species (island speciation).