The .308 will punch paper a whole lot farther than 500 yds. Twice that easily. Many a man has died at ranges beyond 500yds, from.308 holes. More everyday. Check out Camp Perry
Many elk and deer have been put down by the trustworthy.308 as well. There are lots of bullets too choose from. It's all about placement. Holes kill, not impact.
.300WM is in a class all it's own. It can put some big bullets in the boiler room way out there with ease. It comes with a recoil toll. If you want to shoot steel plates at 1500yds or more The .300WM would be my choice. A 225gr. bullet is going to reduce your doping for wind a bit.
If you want reach out and not pay a heavy recoil toll go with a .308. JMHO.