All other things equal...
Bigger bullets kill game better than smaller bullets.
Faster bullets kill game better than slower bullets.
Unfortunately, it's a lot more complicated than that....
Not really:
Big is a sufficient (but not necessary) condition for good performance.
Fast is a sufficient (but not necessary) condition for good performance.
It follows that
Big=good
Fast=good
Big and fast=really good
Small and slow (BB gun)=really bad
If it is small, it better be fast. If it is slow it better be big.
I think we are saying the same thing.