Engine overhead for dedicated server with UE4 as compared to Unity

I am evaluating the cost of a headless dedicated server with UE4 and comparing the result to that of Unity. So far it seems like unity is more efficient and that too by a very large scale. However, I would like to have more detailed dataset before I conclude. Game is something like Unreal Tournament. PS: When I say cost, I am not referring to the cost of getting a server on AWS, Google, etc but rather how many server rooms I run on a single system. Ignore the game complications, I am only considering the engine overhead cost.

Thanks & Regards, Yash