The problem I see with the 300 is that the heavier bullets don't have enough speed at the muzzle to expand. The lighter bullets are generally varmint bullets not intended for deer. The mid-weights are probably a decent choice at closer ranges. But even those slow to the point past 100 yards where expansion is questionable.
While it'll kill deer with good shot placement and the right bullets I see the 223 with bullets designed for deer as superior.
