Prolog can't scale over large data sets. That's why Datalog was invented. So Prolog has significantly greater capabilities, but Datalog scales better. Your use case determines which one is more appropriate for you.
It's a longish talk, but the syntactic difference between systems like Datomic and traditional Datalog systems is discussed in the video mentioned above: https://www.youtube.com/watch?v=8rRzESy0X2k