So, I guess the answer is whichever caliber you fancy, that you are comfortable shooting, and that you have confidence in.
The .50 caliber has proven itself to be an all around caliber for target shooting and for hunting North American big game. It is the largest selling caliber in the US. However, to me, it is a nothing choice. I have never cared for it, and subquently, I have never had one that shot well for me. I'd stay home and watch golf on TV before I went out shooting or hunting with a .50. Like I say, it's just me, being my typical non-conformist self.
I have shot .54's since I my first rifle, a T/C Renegade, in the early 1970's. I love that caliber, I am confident in that caliber and I am sure I will always have one to call my own. If I were to go out hunting deer or elk, I would take one and I believe it would do the job.
.58's? Well, I really never had one and have only shot a few. From what I have seen, they do OK, but no experience with them.
As we are working our way up, I gotta say the .62 is a fantastic all around choice. With the right stock design, they are comfortable to shoot, even with heavy powder charges.
My very favorite rifle that I have ever had was an English Sporting Rifle in .72 caliber. Comfortable to shoot even with 200 grain charges. And talk about whompability - it tipped a buffalo over onto its back at 100 yards. Ufda!!
Bottom line - whatever rows your boat - go for it.