In a way, most calibers are redundant. Like was previously said, bullets matter more then caliber. ELDX, ELDM, TMK in that 6.5 will kill an elk every single time you put it in its lungs. No need for anything bigger, but that doesn't mean you can't. I have 338 RUM, 3 300 WM, 6.5 PRC, and a 7 PRC and a 6-6.5 PRC being built...so I also get having options.
A simple 223 with 77 TMK's can kill anything you want. To me it comes down to your personal hit percentage, trading off recoil, BC, and muzzle velocity.
I am going to clear my safe and keep the 6-6.5, the 7, a 300 WM, and my 338 RUM even though they will all do the same job. Likely my 6-6.5 will be my CA go to rifle with my 7 PRC being out of state.