I've had a PM9 for a number of years... Excellent little gun. And I recently picked up a P938 Nightmare... Also an excellent little gun.
It's better to have a gun like this than none at all, but I would never consider these pocket nines to be adequate primary defense weapons. While better than nothing, there is nothing like a G19 or comparable weapon when the chips are down and you only have a handgun to see you through.
Remember the reason you carry a gun.... to help you face up to the worst evil in your darkest hour; carry more gun/capacity whenever possible! If you have to pull a gun in self defense, you will be wishing, hoping, praying to have a highly shoot able gun with high capacity in reserve. You don't want to find yourself at slide lock (because carrying a very small gun was more 'convenient') when evil is in front of you and still reigning terror on you.