I think .458 caliber trumps them all. In a bolt action you are talking 458 Lott and double one of the 450's.

Here is my argument;
1)choice: midway reloading has 114 different .458 bullets ranging from 300 to 600 grains.

2)performance: a 350 .458 will match a .375 300 grain bullet out to 100 yards, a 400 grain .458 bullet will perform as well as a 400 grain .411 bullet, a 550 grain .458 bullet will come close to 570 grain .510 bullet.
3)cost: if it matters, .458 bullets can be purchased very inexpensively.

If given the choice of two identical doubles in 450-400 or 500-450, I'd take the latter.