Power is instantaneous (HR is notoriously laggy) but Power is not impacted by conditions (weather, temp, humidity, etc) nor by how you feel (if you’re sick, rested, etc) like HR is.
So IMO neither is “better” but each do have their applications if you know what you are doing. For example, if conditions are good and you’re ready/rested for the workout, then power targets are probably better. They are almost always better for short bursts (like 30 sec sprints) as HR is way too slow to respond there. But generally HR works best as a limiter to your workout efforts for longer efforts in varying conditions.
