There is not a "big difference" between either round, any way you care to compare them. One is bit flatter shooting and the other a bit heavier hitting. If you are a guide or PH and absolutely need to stop a charge then I prefer the .458. if you are a hunter wanting more versatility then get the .416. There is enough overlap that either will do double duty.

Phil Shoemaker
Alaska Master Guide,
Alaska Hunter Ed Instructor
FAA Master pilot
www.grizzlyskinsofalaska.com

Anyone who claims the 30-06 is not effective has either not used one, or else is unwittingly commenting on their marksmanship.