Remember that barriers work both ways. If, by some freak chance, you wind up in a gun battle with various cover and concealment between you and your enemy, your cover/concealment will work both ways. If you have problems shooting through it, so will he. The one exception to this is if he's got a rifle or shotgun slugs; in which case, get the heck out of Dodge, if at all possible. (And if you CAN shoot through it, how can you guarantee you'll hit your attacker, and not little Sally next door?)
If you're being attacked by someone driving a car, and decide that taking out the driver then diving out of the way of the oncoming vehicle (a la Rambo) is your only option, remember that windshields deflect bullets -downward-; you have no guarantee that you'll even hit your attacker, much less take him out of commission. If you take out the tires, though, you've just slowed down the car (NOT stopped it), and impeded its mobility. I carry .45 ACP hollowpoint; the hollowpoint should theoretically take a nice circular chunk out of the tire, rapidly deflating it. This won't stop the car, but attempting to steer with a blown tire isn't that easy, much less the fine vehicular direction needed to hit a specific, moving target.
For FMJ.... its penetration is overrated. I found an Oldsmobile Toronado out in the desert once, that had been shot to pieces by hundreds of rounds of 9mm, .40, .223, and .308. Only one round penetrated -everything-, the .308. Engine block, frame, transmission, it didn't matter. The .223 made holes in everything except the frame and engine block, zipping right through the car. The pistol rounds... well... They would penetrate one layer of sheet metal, and not much more. They didn't even make terribly much of a dent on the next object in line.
Sure, if someone were hiding behind one of those doors, you could hit them, but unless the round then proceeded to take out their throat or similar "soft" areas, it wouldn't do them much harm.
Now, if you really, truly expect to get caught in gun battles involving brick walls and Buicks, and want to use a pistol, there IS a gun that MIGHT work for you. The CZ 52. The 7.62x25 round it fires is a high-velocity pistol round that puts a nice, neat little hole through most everything. There's not really any expanding ammo for it, I'm afraid, and it's known for overpenetration of just about everything. Ideal round for someone who shoots through car doors every weekday, and twice on Sunday.

Just remember you're responsible for whatever your bullets hit.
I worry more about whether Joe Mugger is hopped up on drugs than if he hopped in his car. As unlikely as it is any given day for any of us to be robbed/attacked/etc., it's even more unlikely that we'll need some super-penetrating round. Most thugs will back down at the sight of a gun; very few will decided to engage in a prolonged gun battle; and of that few, not many are smart enough to be able to hide behind hard cover and plan out how to shoot back at the same time.
