FWIW 458 Lott brass CAN be formed from other, cheaper, more available brass since it was originally formed from 375 H&H brass by Jack Lott. Also, standard 458 Win ammo/brass can be fired in a Lott chamber (sort of like 38spl in 357mag) in a pinch (not something I'd do all the time, but if I absolutely couldn't get other brass I would).
If it were me, and if the rifles chambering each were of similar cost, I'd go with the 458 Lott, in the CZ rifle. I'd feel well armed hunting anyhere in the world, and if I became seperated from my Lott ammo, I could find 458 Win ammo just about anywhere in the world and use it in a pinch. Seems the best of all worlds to me.
Just the opinion of an armchair safari hunter. I love and shoot big bore rifles and a trip to the dark continent is of course on my bucket list. Right now, the most dangerous thing I shoot is paper targets, lol. Maybe some day.