I'd take the .25-06 AI. I'm not a terribly big fan of magnums unless I really have a genuine need for one. Deer definitely do not require a magnum to kill, and since that .25-06 AI, loaded right, is just about as flat shooting as the .300 Win Mag out to all rational ranges (unless you practice a LOT at extreme ranges like Ridge Runner), and the deer won't care one bit about the difference as it'll be just as dead either way. Might as well go with the lighter weight/recoiling round.

Mike