Do you reload? As already mentioned that could change things. As Dorset Shakari said, the main difference is the powder capacity of the cartridges, as you're pushing the same size bullit in either case. A 7x64 loaded tends to be about circa 150 or so fps faster than a 7x57, with the same projectile.
Now what does that mean in real life then?
- Less recoil where less power is used.
- Your Bullet velocity in the x64 will about the same a hundred yards down range vs what the thw x57 is. So at 300 yards with the x64 your bullet is travelling at the same speed the x57 did at 200 yards.
If you're very much into hydrostatic and hydraulic shock, this might be important to you, i guess.
-, in terms of drop the 7x64 will have you dropping the same as the x57 just around 20-30 so meters later, depending on how far the shot is. Now most mid sized cartridges have a pretty straight trajectory until they hit the 200-250 meters mark, then, depending on the cartridge, they start to drop pretty quickly.
This point will be reached circa 20 or 25 meters later with the x64 than the x57, and at 300 meters your x64 will have dropped to circa where the x57 was at 275 meter and so on.
- the 7x64 will carrry the same energy the 7x57 did about a 75 or so yards further. So at 300 yards your x64 will carry the energy your x57 did at 220 or 230 yards.
But unless you plan to be shooting deer at beyond 400 yards, or use very energy demanding bullets for expansion, i am not sure that's hugely relevant. It depends on your needs i guess.
So basically the x64 , at the cost of increased recoil and powder expenditure, buys you about 25 meter of drop longer distances, it buys you circa 75 yards of energy down range vs the x57 and it buys you about 100 yards of bullet velocity down range.