I would take a second rifle as a backup if you can manage the weight in your luggage. Its a short hunt and you don't want to waste any of it worrying about a borrowed rifle if yours happens to get damaged in transit. That means take the .458 and the .375 as a backup. Either rifle can be used for the lighter stuff. If you take only one rifle, then I would probably take the .458 over the .375, although I might think differently depending on the terrain that you are going to hunt.