One thing's for sure, you'll probably have a lot of choices in either caliber you decide on.
I own neither of these calibers. I'm not an advocate or opponent of either of them. Were I comparing them as you are, I would probably find myself leaning toward the 7mm over the .25 simply because of a wider variety of projectiles available (some with very high BCs) - and because I reload and would probably want to take advantage of that.
I don't own a Savage, Browning (rifle) or Tikka, nor the current batch of Rugers or Winchesters, so I can't speak with any cedibility about the pros or cons of any of them. My Remington 600 and 700s have served me well over the years, as has my Weatherby Vanguard and my CZs. My brother's a Ruger and Browning guy like most of his hunting buddies. Our hunting camp stories seem less about the gun than they are about the person behind it. i can't remember any instance where anyone's had a mechanical problem with a rifle.
It'd be pretty easy to overthink this otherwise. But, provided you wind up in a good quality rifle and scope, your son should be pretty well set for awhile with either of these calibers.
Have you asked him what his preference is yet?