All are good. A .270 is flat and accurate. A 30-06 is versatile and still accurate. But there is just something special about the .308. Oh, and it is also versatile. Over the years I've watched a lot of people make this decision, including myself. I went with the 06, my father went with the .270, and my buddies have went with pretty much every caliber you can think of. With all of our combined years of hunting experience, we've all finally concluded that absolutely nothing beats the .308. All of the other calibers mentioned work so you can't make a bad decision with any of those choices, but nothing works as well as a .308.
Just my .02 cents
I would also suggest you try something other than the .270 simply because you've already had one. Try something different every chance you get and eventually you'll have tried them all, but for everyone I know that road lead back to the .308 (except for one friend, 7mm Mag, but he's not the sharpest knife in the drawer).