Given the .30-06 at 500 yards is going to drop significantly less than the 45-70 cartridge, you don't need much more than that to measure accuracy of the bullets. You need to be the right guy pulling the trigger with both in order to hit what your aiming at. Gravity is constant, figure in the windage and now you realize why so few people are capable of this type of shooting.
If you can't hit a 6" plate at 200 yards with either, it doesn't really matter which one. Just a point, the 45-70 drops about 9" at 200 and the '06 is 1.5" high at that range....
I broke 80 with a $100 set of golf clubs but I can't hit a 6" plate at 200 yards anymore with anything....cept maybe my car!