They were great players at different times, to be honest I don't want to equate or compare these two players, because they were in different times. Benzema has proven that he can survive until now, and Mbappe is a young player with a bright future, but I wonder how he can survive in such tough competition. I mean he has to maintain what he has shown today, and even more he has to improve considering his young age and it is an advantage for him to accumulate a lot of experience which will make him a really great player in the future.
I think he has to brave out of PSG to improve his ability. If he stays in the Comfort zone, he will definitely not develop. He needs a league that has better competition. The level of the French league is still below the Spanish League, EPL. Actually, the decision to leave will certainly improve his ability. But I heard he will stay at PSG, so the possibility of him moving to Madrid is still just a rumour.