Cable nodes work on a round robin frame structure, so it would make sense that fiber has less latency. All bandwidth is going to be shared somewhere, but cable

Cable nodes work on a round robin frame structure, so it would make sense that fiber has less latency. All bandwidth is going to be shared somewhere, but cable is often heavily over subscribed at the node level, which is going to matter more when you are suddenly given more DOCSIS channels but the node is left unchanged.