.380 IS 9mm at close range.
The further out you go the slower it travels. At some point, the .380 will not be enough anymore but the 9mm will still be enough. A little further out and the 9mm will not be enough and you need something stronger.
Far enough out and you need a rifle.
A little further and you need a mortar.
A little further and you would need artillery, and an Air Force would be nice.
I concur with the opinion that skill trumps everything, but I would also add that you have a fighting mindset that applies to this question. What scenario are you preparing for and how does your weapon/tool fit for that scenario? What other important considerations apply to that scenario? In other words, it is perfectly legitimate to carry a belly gun for fighting at beer breath ranges if you are prepared for what actually happens in a fight when you are that close.
On February 26, 2012, Travon Martin lost his life because he jumped on top of a man, George Zimmerman, who had a pistol under his shirt. For many, many years in all the discussion about the shooting incident ever since, there is nobody, and I mean nobody who thinks that George Zimmerman's choice of caliber is what matters.
I like to watch videos at the Active Self Protection channel on YouTube. In all these years, please correct me anyone, host John Correia has shown no situation where a .380 failed when a 9mm would have succeeded. This is an argument from silence which proves nothing. I am just saying you should get ready for what you believe is most likely to happen.