I may feel that a V-8 gets better gas milage because it doesn't have to rev as high as a four banger but when tested, we can look at the evidence and see that this is wrong.
Not always. It will depend on the size, weight, aerodynamics and the conditions driven that will determine which is best for,
each individual application.
For some situations the 9mm will be better.
For some other situations the .45 will be better.
In some the .40 will be better but yet in others it will be the worst of the lot.
Your defense weaponry, just like your motor vehicle should be based on the conditions you THINK you will encounter. Which is why the choices are not, and never will be, the same for everyone.
Another example is clothing. What you wear to work in December may be vastly different than what you choose to wear around your backyard in July.
What they will be wearing in Florida next January will be somewhat different than what we will be weaing up here in Seattle next January.
Thankfully, most of us here, live in a country when you can choose a 4, 6 or 8 cylinder, gas or diesel engine.
As well as a .35", .40" or .45" diameter bore in a semi-auto or revolver.
And best of all, the option to own one (some) from each catagory.
Viva la difference.