That's the sectional density argument you made earlier, to which nobody responded.
The flip side of the armor piercing bullets argument is that if you have two bullets of equal energy then the one with larger diameter will impart more energy to the target than the smaller -- the smaller may pass through the target (carrying energy beyond the target) rather than staying in the target and distributing the energy internally.

There is no one-size-fits-all answer. But in close quarters fighting (urban warfare) you don't need long gun accuracy or down-range energy. Worse, with high velocity rounds in a ricochet-rich environment, everybody is in danger rather than just the enemy.