I know from somewhere that project dependencies on a specific configuration are discouraged and variant-aware resolution should be used instead. Can somebody help me find specific reasons why, since dependencies on specific configurations are much simpler?

I think it's mainly that configurations are meant as "implementation details" of the build, and variants as their "public API". Fwiw: https://docs.gradle.org/current/userguide/cross_project_publications.html

Thanks, this is the explanation I was looking for.