That's a couple of good points there. Powerful does suck to shoot. Spend a day on the range firing 50 cals and you'll feel it... Effective is also typically a smaller caliber for a few reasons. Sure, recoil being one, but also when a large powerful bullet penetrates someone's body, it goes in and out and leaves a hole. When you shoot someone with a .22 the bullet penetrates but a lot of the time doesn't have the power to go right through and turn everything in it's path into a hole. Instead it bounces off bones and ricochets around in the body turning your insides into soup. That's why in a lot of scenarios a smaller caliber bullet can be much more deadly.
I'm sure you already know this BayAreaCoins, but it seemed like a valid talking point.