"better" is a subjective term unless you state the nature of use, the action, your skills and ammunition to be used. both do what they are intended to do.
Depends which 7mm your talking about. The only 7mm I know of that has a larger case capacity than the 300 wby mag is the 7mm Remington ultra mag or 7mm rum
100-300
yes
OK
300 USD
Value about $300-500, depending on condition, and the exact model. There were Several Mdl 111's in 7mm Mag.
300 or so
Depends on the model and condition, but about $300-$375.
Gun shop, gun show, want ad
It should be marked on the barrel. There are other 7mm rounds besides the 7mm Mag.
Personally I think the 7mm ultra mag is the best choice of weapon. It really depends on what you are doing with it. The 7mm ultra mag has very little drop and is an excellent long range weapon.
300-700 USD