30-06. Lots of variety in sizes of bullets you can use and it is just a better elk gun. Sure, thousands of hunters take elk with a 270 every year, but if you have a 270 and a 30-06 both in your gun cabinet and you are going elk hunting, you will pick up the 06 every time. If so, why not get one to start.
I get the Reduced recoil 125 gr bullets for my 06 for young kids to shoot. Kicks like a 243. The 06 just has a wider range of things it can do.
Or just do like me and get both! There is not a finer deer gun on the planet bar none than the 270.