From someone who owns a 416 Rigby (Ruger Bolt) and a 458 wm (brno bolt) on the bench, the 416 is more severe, but when shotting off hand at a buffalo i wouldn't be able to tell the difference. I hate shooting my rifles at anything other than a trophy, or meat (or a bit of fun).

The 416 is more of a big push where the 458 is a sharper kick.