I think it would depend on whether the journey was the objective, or if I needed to be in Moz for some reason, and the journey was just to get there.
The reason for that is simple. Shooting a buffalo if you're on your way somewhere is going to result in a huge waste of meat. You can certainly eat your fill, and maybe carry a few days supply with you, but you would leave most of it to rot. More likely, you would be shooting impala and small plains game, so that you can have fresh meat most days, and carry a bit for the days when you don't see anything. For these, my .300 WinMag would be ideal. Lighter than a bigger bore, but allows you to take pretty much anything short of buffalo, rhino and elephant (although in a pinch, if I was a Bell-type shot (which I'm not, but since I'm dreaming, sure, of course I am), then it could work on those animals as well).
On the other hand, if I were taking my time, seeing the sights, walking and then spending time in one place or another, and especially if there were a few of us, then larger game might make sense. In that case, I would have a .416 Rigby, which will still allow me to get some plains game at reasonable distances, but also the bigger stuff. And I'd have help carrying the heavier gun and ammo.
As for charges, neither of these rifles is really a charge stopper, but if I don't shoot at things I shouldn't with my .300, then I shouldn't have to worry about charges.
If I do worry about charges, then I should be moving up to something like the .450 Rigby, the .458 Lott or bigger. But those aren't very useful everyday rifles, so for the purposes of this question, I choose never have to deal with a charge. Or, better yet, stop worrying so much.
Bullets would be Barnes in all cases.