Can you give some more criteria?
Are you a handloader, or will you be using factory ammo only?
Some calibers offer alot of good factory ammo, others will likely need to be handloaded.
One example would be the 270 vs the 6.5-284. They are very nearly identical in performance, but the 270 will shoot ammo you can find in any store in any state at any time of year. The 6.5-284 really needs to be handloaded because there just isn't much factory ammo for it yet......yet is the key word IMO. I prefer the 6.5-284 because of higher BC's and less recoil, but I am a handloader too.
Buying a factory rifle or building a custom one?
Optimum LR performance usually means shooting heavy bullets for the caliber. Most factory rifles still haven't caught on to that yet, some have. Heavy bullets mean faster barrel twists than alot of factory rifles have. Optimum LR performance often can mean a custom barrel with a fast twist rate.
Lets take the 270 and the 25-06, both excellent antelope guns. Compare them to the 243 or 6mm remington (also excellent antelope guns). The 270 and 25-06 rifles usually come from the factory with twists fast enough to stabilize the common heavy bullets in those calibers. However, the 243 and 6mm really really shine with 105 and heavier bullets that need a twist of 9 or faster.....most factory rifles are 10 or slower.......not all, but most. Shooting a 115 VLD in a 6mm ballistically equals and even outperforms most of the 117 bullets in the 25-06 at long range, but it usually takes a custom barrel with an 8 or faster to shoot the 115gr 6mm.
Some will get on here and tell you that you need some sort of 7mm super magnum for antelope. Then they'll say you can put a muzzle break on it to tame the recoil. Muzzle breaks only work if you're willing to put in hearing protection each and every time you shoot it. In contrast, most of us can easily handle a shot or two through a standard barrel non magnum cartridge (no brake) without hearing protection in a hunting situation, and not even know we fired a shot. A muzzle break will definately let you know you fired a shot, and your ears may tell you about it for many weeks after the fact if you don't have protection in.
Are you the type of hunter that will diligently put on hearing protection each and every time you fire a shot?
Final question, Is this gun going to be used for antelope only, or maybe deer too? Or is it going to be antelope and strong possibility of elk, moose and bear? Or, is it mostly varmints/predators/targets and antelope just once a year?
What's a good caliber for elk is not a good caliber for prarie dogs. A good caliber for antelope out to 700 yds is not necessarily a good caliber for elk out to the same distance...........It really depends on what your intended uses are and what style of hunting you do.
If you answer back on the questions above, you'll get much more meaningful responses from this site.
Welcome to LRH, Oh, my 2 cents is 25-06 by the way.