I've recently owned both and think you made the right decision for the right reason. I loved both rifles equally, but I have to say that the Weatherby just felt a hair better for me when shouldering. That's just my preference. The Tikka was also outstanding. It's splitting hairs, really......and completely subjective. In my opinion, though, that's something very important and could be used to break a tie so to speak......assuming one exists. If you can close your eyes, shoulder it and even track with it a bit and just feel how it fits\sits. Does it feel forward heavy? Clumsy? LOP feel right? Check weld feels good? Does it shoulder quickly and comfortably? In all honesty I don't believe you can go wrong with either. I've also got a few Mark V's, though, so maybe that helps with the Vanguards for me, too? Either way. Congrats to your friend on a great purchase and kudos to you for giving him a hand with it as well!
Mine was chambered in 30-06 and didn't shoot anything poorly. Shot CoreLokt, Fusions, SuperX all to around 1 inch. It did, however, especially really like anything by Nosler and Sierra. Game Kings, Nosler Ballistic Tip and Accubond in 165. Those were all very easily under MOA and on a calm day and me shooting at my best I could get 3 shot groups with very close to 3 holes touching. Outstanding for a factory rifle with factory ammo. It was boringly consistent with those rounds. Never tried anything heavier in those. If it were me, and if I was breaking the rifle and sighting it in, I'd start with either Federal Blue Box or Hornady American Hunter. They're cheap and who knows? One of those could also surprise you. Once you're done sighting-in the first 2 boxes of factory ammo that I would personally try are Game Kings and Ballistic Tips (or Accubonds if you're wanting\needing it). That's just my $0.02