What has better armor penetrating potential?

Neither. Go to the NIJ website; they've got lists of what each level of vest is rated for. Neither of those calibers are good for penetrating body armor. The best common caliber for vest penetration is 9mm, which will pierce lighter vests with hot loads. No kevlar vest will stop rifle rounds, though ballistic plates will.

Murphy also factors in; you never know when someone might pop off a lucky shot that hits the vest just right to pierce it. Alternatively, and more commonly, maybe the vest is hit at such an angle it stops a threat it's not rated for. Ballistics is a funny thing.

Of the 2 options, the .40. Smaller and faster for the same projectile make = more penetration.

But your question is like asking what makes a better racecar, a ford minivan or a chevy minivan... They both suck compared to hundreds of other options.

Neither will penetrate armor. Go with the 5.7 or a rifle round.

it isn't the caliber that you should be thinking about, its the projetile. Unless it is properly shaped or constructed, neither caliber will fire a projectile that wil defeat body armor

Neither. Go with a FN Five Seven or .22 TCM.

45 ACP...... It delivers a lot more energy.......