there is no question that a .243 is a good round, and yes it is a "better" round than the .223 BUT...... given the fact that he also wants to plink with his gun, the .243 factory ammo is NOT CHEAP (about $15-20 per box)....
Since he doesn't have deer in his hunting list, I think he can't go wrong with the .223, cheap ammo, GREAT ACCURACY, oh, and fun as heck to plink.