A good friend who goes to the Dark Continent to hunt things that bit and stomp has a much loved 450 Ackley custom rifle. But his most recent purchase was a 458 Lott and the Ackley is now retired. His explantation is that the Lott is more powerful than the .458 Winchester but can also chamber the .458 Winchester should Lott cases not be available. He also says the Lott is a straight walled case which loads and feeds better than the bottle-necked Ackley.
Both cases are based on the .375 H&H, with the Lott being 3/10 of an inch longer than the 458 Winchester. The Lott was developed in the early 70's while the Ackley dates back to the 1960's. Both were an attempt to provide a little more power than the .458 Winchester. The Ackley is more powerful and puts out a 500 grain bullet 100-150fps faster than the Lott from barrels of equal lengths.