That is one very hard question to give a straight answer too

Both are great calibers and they both overlap one another up to a point. I suppose it will all come down to the size of game you wish to hunt and the terrain you are going to hunt in, as far as heavy bullets are concerned the 30-06 has the edge. As for the run of the mill bullets used in both calibers 150-168gr there is little to choose between them give or take a 100-150fps. Animals dont seem to notice the differance when hit in the right spot with either. The only advantage to me is in the design of the rifle and action lenghts for the two calibers in factory rifles. The 308 has a shorter action and bolt throw than the 30-06 has, it may only be a split second faster, but that is sometimes all you get for a follow up shot or shots, especially in Europe durring driven hunting. If you are a mountian hunter the 308 can be built slightly lighter and shorter than the 30-06,not much but after a few days it all adds up. Another reason I enjoy the 308 more is that it has less recoil than the 30-06 in a rifle of similar weight. Once again it has nothing to do with being recoil shy or the 30-06 being a heavy recoiler, it is just faster to regain a sight picture with the 308. Dont know about there, but here 308 ammo tends to be cheaper. I have seen both take big eland down when used with premuim bullets. All going to come down to personall preferance. I am sure other members will have more advice and experiance with both calibers. Good luck making a hard choice