PoE can't do "purely" DC/DC regulation. They require (in any reasonable setup) a transformer for isolation on both ends, which lowers efficiency, especially at

PoE can't do "purely" DC/DC regulation. They require (in any reasonable setup) a transformer for isolation on both ends, which lowers efficiency, especially at lower end. Now with that said you can definitely get decent efficiency with PoE, it's just that most people don't care and so it's not as big of a focus.