My advice is to make the choice based on actual rifles rather than the calibre. A .458WM built on a standard length action makes for a really handy rifle, whereas a Lott requires a long actin like the Brno 602/CZ550 - which I find a bit unwieldy. Pretty much any 450grn banded mono can readily be driven to 2200fps (or even a bit more) in a WM built on standard length action. This is makes a great load for giraffe, hippo, buffalo and even elephant. The Lott can accommodate 500grn monos at about the same velocities., which makes it more flexible - but at a cost of increased size and additional recoil, If using 500grn bullets in a WM then its best to choose a bullet which has some lead as 500grn monometals will result in powder compression unless seated very long (only possible in some rifles). With an appropriate lead core bullet (like the Woodleigh) you can expect to get around 2150 depending on a number factors, including barrel length. Barrel length on .458WM should ideally not be less than 24" unless you plan to use only 480grn and less. With the Lott you can cut the barrel to 22", obviously at a cost of some velocity - in all likelihood making it perform much like a WM with 24" barrel. So, as I said at the outset, I would advise making the choice based an a particular rifle rather than the calibre per se.
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