270, 308, 30-06, and 7mm08 are all so similar in nature ballistically speaking they are equally good at getting the job done.
Shoot your chosen caliber, and learn it's limitations. Being familiar with the gun and the round matters more than anything when you are thinking about making a tough shot. You tend to make less risky shots when you are confident with your hardware.
Why? You know you can sometimes wait just a bit longer for a better shot that you know you can make.