Hi Zulkarnain,
I completely agree with Atul. I think he is right in saying that For a system our gain should be optimum and yes it is the gain that decides efficiency as i had also mentioned in my previous comment but yes in practical systems gain needs to be of optimum level because non linearities would come into existance. I also agree with him saying that that it is the fact that high power is one of the techniques to increase the gain efficiency of the system.So there shouldn’t be any of the confusions now. I hope it is helpful to you.
Regards