Not saying .45 is a bad caliber, but the "bigger is better" argument is akin to the "I only run 55w80 HDEO in my Civic because heavier is better" argument. Just like any tool, you have to pick the one that fits you and your application.
And smaller ammo can be pretty effective in and of itself. Case in point, .223.
And smaller ammo can be pretty effective in and of itself. Case in point, .223.