What kind of scope is best for a 7mm Mag?

Last year I won a Rem 300 Win Mag at a gun raffle. When I got it I put a VX-II 4-12x40mm AO on it. This year I was lucky enough to walk away with a Weatherby Vanguard 7mm Rem Mag with stainless steel barrel. I need some suggestions on a scope to put on it. I was thinking of just getting another VX-II 4-12x40mm AO. A friend of mine told me to go bigger on the 7mm. While another told me to take the VX-II 4-12x40mm AO off the 300, put it on the 7mm and then go bigger on the 300. Anyone have a suggestion? Right now my max shot would be 100 - 150 yds but if I go out west in the future I don't want to have to purchase another scope. I want something I can dial down for now and then use for long range later.