Brutus, im sorry, but you couldnt be more wrong(I would have called you an idiot, but that would be abusive)
The 7mm Rem Mag. Is MY choice of the three, BUT, the 300win Mag is ballistically superior to the 7mm in velocity and energy.
In comparing the 7mm and the .300 with 150 gr bullets at 500 yards, the .300 has 10 fps more and 10 more ft lbs energy, you go heavier, the 300 wins all out.
The .270 is no comparison to either of the bigger rounds.