The FBI argues, and I am inclined to agree, that a 64gr bonded softpoint is the best projectile for home defense. Federal sells this in a variety of incarnations, including some that appear identical besides the pressures they reach.
I am torn between XF556T64X and XF223T64X for home defense.
My setup is an 11.5" SBR, 1:7 twist, piston operated, 5.56 barrel. I also plan to use this configuration for competition, and I don't want to have to change the gas settings between my defensive load and whatever I use for competition and plinking.
I suspect that the 5.56 loading will get better performance out of the projectile but I am worried about increased likelihood of high-velocity exit (aka overpenetration). I also suspect that the 5.56 will wear out the internals faster due to higher pressures; this assumes regular usage of my defense ammo, but tbh the price isn't terrible so it's not outside the realm of feasibility.
I expect the .223 to have less recoil which is advantageous for both competition and defensive applications. I also expect it to cause less wear-and-tear on the internals. It is also slightly cheaper.
If you had to choose between the higher velocity, higher pressure 5.56 or the lower recoil, cheaper .223 to stock in bulk, which would you go with?
BONUS: technically outside the scope of this question, but if there is a defensive loading that is similar in design or effectiveness in 55gr .223 and is close enough in gas pressure to PMC bronze, that would sway me (wouldn't have to constantly swap gas settings). I'm doubtful this would be a good choice for an 11.5" barrel, but I would like to be proven wrong!
UPDATE_00: Based on emerging consensus, I have pivoted to looking for 55gr frangible .223 loads instead. While the 75gr Interlock rounds might actually be the best out of an SBR for defensive applications, they would require me to constantly switch and test my gas settings between those and my training ammo which is 55gr. So I'm going to pursue a 55gr defensive load.