Tell him to get the 243. I have had lots of friends ask that same question. Invariably they get the '06 because it will be big enough for elk....which they NEVER get around to hunt. The lightweight '06 kicks like a mule and consequently they don't shoot it enough to be familiar with it when they hunt whitetails. A nice lightweight 243 is something that they can punch paper with and maybe some varmints and they will be happy to use if they go after deer or antelope. If the elk hunt ever happens they can go buy a used '06, there are always lots of them for sale.

“My horn is full and my pouch is stocked with ball and patch. There is a new, sharp flint in my lock and my rifle and I are ready. It is sighted true and my eyes can still aim.”
Kaywoodie