The simple fact is that none of the 300s can be outright proven to be better than all the others.One person may consider the fact that one has a wider variety of factory loads to be an advantage,while to a handloader it means nothing.One person may argue that one cartridge has been around longer than another,but a longer history doesn't make the ballistics any better,and it doesn't make the cartridge kill any better.A shorter barrel life means nothing to the person that shoots ten or twenty rounds per year,but it may be important to the person that shoots 500 or 1000 rounds per year.
It all comes down to everyone choosing the cartridge based on their own criteria,regardless of what other people think about the cartridge.