"Casting" is screen mirroring ("Casting" is Google's word, I think that "screen mirroring" is Samsung's.) In non-technical terms, what are you trying to do, and what are you getting that;'s not the thing you're trying to do? (Both MHL and Chromecast will put the phone's screen onto the TV screen, and the phone's audio into the TV's speakers. And that's it.)
(If you're trying to see where your finger is by looking at the TV screen, you won't.)