My buddy (ask him if he is not my buddy
) Melvin will tell you "You cannot kill it if you cannot see it!!!."
Anyway, Melvin really likes Leupold scopes and I suspect that he will advise you to use the VX6 or perhaps the 4.5-14X40 with my B&C reticle.
If you were to buy a .308, he'd probably advise the wonderful Leupold 2.5-8, but a .300WinMag is entirely a different critter.
Choose whatever you want, but do not be a "slave to tradition" and buy the scope that will make you happiest.
Blessings,
Steve