To my mind the biggest argument in favor of the 458 Win is that it doesn't require a massive action in order to work properly. This means it can be made up into a lighter, slicker rifle that is easier to carry and that will make for a shooter who is less fatigued and quicker to the shot when the shot presents itself. If you're going big why not go all the way? If 150fps with a 500gr bullet is enough for you to want to lug around an extra pound of rifle, why not go with the 505 Gibbs? No compaction problems there...
