How can they not be better if they remove the need to burn a bunch of power 24/7 and produce waste heat? It's replacing an ongoing cost with a fixed one. In both cases you need a hardware investment (PoW mining hardware for one, persistent storage for the other) but the proof of work system ALSO has a large ongoing energy cost in addition to hardware.
GPUs or ASICs for hashing are going to have a limited life span just like your storage hardware, too.
