I didn't read all the posts, so I apologize if this is redundant.
I prefer whichever one penetrates the best, and yes, that means FMJ ammo is fine with me. I don't care in the least about expansion because I assume none is going to occur. The FBI shootout in Miami was prolonged because someone's 9mm stopped about an inch short of the worst of the two bad guys' heart on a sideways shot that went through the right arm and entered the chest cavity but didn't make it to the heart. It was a fatal shot but not a stopping shot. I believe that possibly cost two cops their lives. I want to make two holes with one shot, whether I have a frontal or side shot. That way if there's anything in that path worth hitting, it will get hit.
No worries about over penetration, either. Missed shots are the ultimate in over penetration, not being slowed down at all, yet cops and civilians alike fire them in abundance. The percentage of hits in a gunfight is surprisingly low, so the odds of you having a miss or two is quite high. I would guess this comes from the lack of ability to hit a moving target which is not very easy to practice on a range.