I love the 7MM Rem Mag. But if you have a 300 Win Mag, a 7MM Rem Mag won't fill much of a purpose other than to say you have one.
I know they aren't a lot better than a 30-06, but I still think the 7MM Rem Mag is the ultimate deer gun.
That's my opinion, and I am entitled to it.
I love the 30-06 as well to be honest, and it is still the most popular centerfire cartridge.
Now there I said it loud and clear for all those 30-06 guys who think you don't need a Magnum. I'm not arguing that you do.