I just bought a Tikka Whitetail Hunter in 7mm and I really think it' s a great gun. Guarenteed 1" MOA and the action is like silk. Trigger is adjustable between 2-4 lbs. and very crisp, clean break. Got mine in stainless with laminated stock and detachable external magazine.

As far as caliber, either is fine. I doubt there is any significant difference between the two really (.308" vs. .284" = .024" ). Best thing you can do is shoot both and see which one you handle better, preferrably in similar guns so they react according to the caliber and not the rifle.

BTW, the Tikka T3' s are not as good as the Whitetail models. They feel cheaper (and are less expensive) so make sure to find the brand you like before you look for caliber.