In short, the answer is "yes" if you are thinking of the topic from a strictly hardware perspective. If you have to defend yourself from a potentially deadly attack, being armed with anything less than a tank is sub-optimal. But life is all about balancing risk vs reward and using the tools we have. Very few of us have tanks at our disposal.
So instead we choose a firearm, as it's a tool that is powerful enough and portable enough to use day to day. Maybe we have a small firearm we carry every day, or have available in the home, like a handgun. Maybe we have a rifle or shotgun available at home for defensive purposes. We each have to choose a tool that works well for our given situation and balance risk vs reward. If we have children about, keeping guns locked up is an imperative. What methods we have to secure firearms certainly plays into the equation.
But in this post I wanted to cover two topics. First, criminals in general tend to be poorly armed. The streets are awash with illegal guns and little knowledge about said guns. Except for rare instances or organized crime, criminals tend to not have lots of ammo on hand or the most modern, durable and reliable firearms with them. This is for a couple reasons.
First, many criminals that carry guns are legally prohibited from owning guns. Misdemeanors of domestic abuse and felony convictions remove a citizens right to own guns. Cities like NYC, Chicago and Washington DC where we see the highest violent crime rates all prohibit citizens from carrying guns. (unless you are politically connected, that is) Because carrying a gun is an illegal act for many people who end up using them in crimes, they tend to not invest heavily in guns. They find something cheap that is good enough, since in any interactions with police they will have to discard the gun or have it taken from them and potentially brought up on charges.
Second, the areas where most of these violent crimes take place have much tighter controls on guns, ammo and gun shops. The city I live in, St Louis, hasn't allowed the opening of any new gun shops in city limits in decades. This limits poor people's access to legal guns, driving them to black market guns of questionable serviceability. If your choices for purchasing guns comes down to 2 pistols for $100 out of somebodies trunk, you are going to experience a higher failure rate than if you purchased a gun at a reputable shop.
Here is an article that breaks down the types of guns used by criminals. You may be shocked to find out just how many were unloaded or in poor working order.
The second topic I wanted to discuss is the effectiveness of handguns. In short, they aren't terrible effective when it comes to terminal ballistics. (terminal ballistics is the study of what happens when a bullet enters a body) If 9mm was an effective caliber for quickly bringing about death, there would be hunters using it to take game. But it's not. Hunters use cartridges that are much more powerful. But firearms chambered in common hunting calibers are often not practical for use in self-defense situations.
This is why training is key. A hit with any caliber trumps a miss in something more powerful. It's also silly to get wrapped up in choosing the ideal handgun cartridge, because none of them are ideal. All handgun cartridges are compromises, and being able to hit your target is the most important part. On that note, here are some real world statistics on the effectiveness of different cartridges.
Training and practice is what matters. Time spent researching the ideal cartridge when you could use training and practice is time wasted. Use the gun you have and get really good with it. Take a class or two. Schedule time for practice. That is how you can be best prepared to defend yourself.
The tool you have is less important than your mindset and your skills when one is considering whether they are undergunned. It's not about the equipment, it's about the individual.
I'll end this post on a humorous note with a youtube video, one suggesting the inner city demographic likely to be involved in crime can't shoot. Take this with a grain of salt, I know that I did. :-)