Personally I'd say seperate them, have the healthcare have a simple follow script in a custom update or tick method and move it to the new position, this way you can control when you need to move it
#Relationship between enemy and its healthbar in Unity
zenith oyster
spare pelican
How is this different than the other question you asked?
molten river
Please don't write a second post about the same problem you posted about on the same day. It confuses the rest of us and needlessly clutters the forum. Sure you clarified that you already knew how to do it both ways, but it has barely been four hours since your last one. I feel it would have been better if you added this clarification to your last post, bumping it, instead of making a new one.
But enough about forum etiquette, as to which runs better on the player's machine, I honestly don't know. Unity does give you two, maybe three, tools to help you figure that out for yourself though: the console window, which helps you spot errors; the profiler, for looking at cycles per frame, and the memory profiler to track ram and memory leaks (this third tool is still in development so may not be as reliable).