More for you to consider.
The 6.5 will be spinning faster with the typical 1 in 8 ROT 6.5 CM and 1 in 10 ROT 270 Win. Does rpm matter on impact with game? It's certainly not going to be less....
Obviously, 500 fps is a lot.
Does recoil matter to you?
Higher bc will drift less, always. No matter the distance.
Prediction. Doesn't make a darned bit of difference on game because bullet placement is what matters.
Nor sure where you're coming from on the higher B.C. thing. Velocity plays a big part in wind drift.
Take the following examples using Nosler data:
.625 B.C., 6.5 CM, 144g ABLR @ 2731fps
.530 B.C., 6.5-06, 130g ABLR @ 3151fps
.591 B.C., .270 Win, 150g ABLR @ 2913fps
The 6.5CM has the highest B.C., yet it has the most drop and drift and least velocity and energy out to 1000 yards, the limit of my range calculations.
