After all the talk about calibers that are so similar in ballistics you have opened another can of worms with glass! I have to say choose the best you can afford. I have a Burris Fullfield II 3-9x40 with the ballistic plex mounted on a Rem. 742 BDL 30-06 and love it. The ballistic plex is calibrated to match the trajectory of the 30-06 and 308 win. with 150 to 165 grain ammo. It has reticle cross marks that correspond with 100, 200, 300, 400, and 500 yards! And it is very close to that with my rifle.
The glass is very clear and works well in dim light and rain. Also check out the Nikon lines with the BDC reticle. (Bullet Drop Compensator) Many optics companies offer the compensator reticles. Check out web sites for Alpen Optics, Vortex Optics, Burris, Nikon, and Leopold for mid priced scopes. And Ziess and Swarovski for high end. Go to the stores in your area and look THROUGH the scope not just at it. Compare different brands and check the specs. All of our opinions are just that OPINIONS!!! I have been shopping for a new scope for long range hunting (600 plus yards) there is a lot of info to sift through. Good luck p.s. I believe that the ballistic difference between 308 and 30-06 is not worth arguing about nearly as much as the bullet choice. Ask any grizzly guide if he wants a hunter with a 340 weatherby mag that flinches at the trigger or one with a 30-06 that puts every shot on a dollar bill ?