Unless your rifle is extremely accurate and you are an expert and can shoot it to it's potential you'll not notice any difference between the 2 cartridges for any practical purpose. They both kill medium big game well. The 7mm is a little easier to develop reloads for and you can get heavier bullets to shoot larger game with it.

Robert, Ballistically if you run 140's in both you'll have a bit more FPS out of the 7 and a better BC out of the 6.5. The 6.5 should have a very slight edge (couple inches drop and windage at 450 and the advantage increases) at distance. Thie is because of the inherent higher ballistic coefficient of the 6,5 Creedmoor. The only advantage of the 7mm-08 is the ability to run heavier bullets for hunting.

6.5 has a the range advantage, might even be more accurate, and has less recoil. "The two have essentially the same velocity and energy out to 500 yards, statistically nil. The difference is the Ballistic Coefficient on the 6.5 is much higher, resulting in a straighter flying bullet. Check the wind drift in the link below. at 1000 yards the creedmoor drifts 5 inches less with only 2.75 inches more drop. Drop is much more predictable to adjust for than drift. The 6.5 also has a much higher sectional density, giving it greater penetration. All things being equal, SD is what gives you killing power. The 6.5 Creedmoor has one of the highest sectional densities in any hunting round, including the 7-08." info: msrhunt.com/post/6-5-creedmore-vs-7mm08-7587152

not enough difference to mean any thing. for hunting they are both 5-600 yard calibers (slight edge to 7mm-08) for paper they will both do good at 1000 yards (slight edge to 6.5) also throw in the 6.5X55 which I like better than either of these