This video gives a basic overview of Lionel's command systems from the first TMCC 1 with Powermaster, to TMCC Command base, to Legacy and combining the systems. As a non-command guy that wasn't paying attention to the hobby during the advent of command control, this video helped me understand how it all fits together and make sense of the advice above.
Another consideration for you is to get him a Lionchief Plus locomotive that he could try out to see if he likes using a remote. If he does like it, consider upgrading to a Legacy system or more LC+ locos. If he doesn't you can still use the LC+ loco conventionally.