"The Best" can be determined by the shooter. Recoil, cost of ammo ( or reloads), killing range, killing power differences, cost of the rifle brand, etc. are a few choices that may enter into the choices.
The 350 Legend vs. 450 Bushmaster is a mere 20 gauge vs. 12 gauge choice.
I prefer the increased range/power of the 450 BM, since the recoil and other costs of operation are of no consequence to me. I like the increased ballistics of a 250 Hornady FTX bullet @ 2550 fps. So far, I'm 4 for 4 deer kills with this cartridge.
One thing that the shooter has to keep in mind with larger or more powerful "big" rifle cartridges is "meat damage". A shot placement through the lungs will not damage any meat. However, an angled forward or away will greatly increase the loss of at least a quarter of meat. That same shot will definitely put the animal down, but at the cost of meat loss.
The cartridges I'm referring to as "big" are: 450 Marlin, 444 Marlin, 450 Bushmaster, 45-70 Govt., 458 Win., 458 SOCOM, 50 Beowulf, 460 S&W, 405 Win., 50-90 Sharps, 50 Alaskan, 375 Win. and 500 S&W.
All of the pistol/rifle cartridges will kill deer with good shot placement, inside 100 yards and possibly further with consideration to the shooter's skills. These are cartridges are: 44 Mag., 45 Long Colt, 45 Win., 44-40, 357 Mag., 41 Mag., 10mm, 454 Casull, 460 S&W and 500 S&W. There are several brands of rifles in single shot and lever-action that are available in these cartridges. They make for low recoil, light weight and easy to handle in the woods type of rifles for all ages.
Good luck with your choices!
Bowhunter57
