Of the calibers you mentioned, I would select the .300 Win Mag. The .300 WM has a greater selection of factory bullets over any of the short magnums. I would choose .300 WM over the 7 MM Mag because of the handloading opportunities should you ever go that route. There seems to be more bullets for .308" than .284". All the calibers on your list, as well as those mentioned in the replies are top notch.