Just my 2 cents--

I have no African experience and little game experience with 458 "heavies" (limited to one bear), and thus speak only what I have read but I think that velocities above 2300 in 458 caliber may be wasted due to the excellent sectional density of the 500 gr bullet(.341)At 2300fps this high SD bullet penetrates well enough indeed. At faster velocities(2500) is not all that excess energy just blowing thru the animal and putting energy into the backstop behind the animal?

Does the 450 Dakota overpenetrate on DG with good 500 gr bullets??

Thus I would take the 458Lott over the 450 Dakota. If I wanted to use a higher energy cartridge I would go for a larger caliber like a 500 A Square shooting a 600 gr bullet(decent SD) at 2200 or there abouts.Just MHO, and I hope not to offend.