True. It all comes down to what bullet is fired from a specific caliber. Supposedly some Spec Ops groups in Afghansistan are using Black Hills ammo in 75 grain (I think) because they have been found to be more effective than the SS109 bullet. A normal FMJ bullet won't do much (but ANY pointed FMJ bullet will yaw after impact at sufficient velocities) but, for example, the West German 7.62 would fragment exactly like the M193 5.56 round- and be far more effective in doing so. Also, if it takes two to three times as many smaller rounds as one bigger round to take down the BG then weight and capacity issues become mute. Besides, it still does come down to accuracy and trigger control- no round will do anything if you can't hit your target!
BTW, I like both calibers with the right bullet....