First, let me say that today's premium ammo, in all calibers is better than what was common 40 years ago, as far as bullet performance/velocity is concerned. Todays expanding bullets are simply better at expanding than what was available back then. And, what was available back then is still available today, still working as well now, as it did then.
I said that to make a point, now also consider this, 40years ago, while there was a bit of debate, it was generally thought (and written about) that the standard .38 SPL was a better defensive round than the standard 9mm Luger.
This was because of the bullets and loads commonly available. Reliable JHP ammo was, mostly, still in the future. 9mm+p+ only existed in the guns of certain handloaders. Factory auto pistol ammo was almost exclusively FMJ, and revolver ammo was lead bullets.
The simple fact was that a heavier, slower, factory lead bullet often performed better in defensive use than a FMJ. There was usually at least some expansion from the lead slugs, and sometimes pretty good expansion.
Today, the lesser calibers are much better than they used to be. .38 SPL velocities haven't upped much, if any, modern bullet construction is what has improved the .38SPL most.
And not all loadings are the same, nor are the circumstances of firing the same. Currently, you can even get factory ammo tailored for the best performance from short barrels, something that was once only possible from handloads. Way back in those days, it was found that the 200gr LRN .38, fired from a snubnose (2") wouldn't reliably penetrate a regular car windshield. The 158gr LRN, (from a standard 6" police revolver) got nicknamed the "widowmaker" because of its lack luster record in gunfights. And even with all that, the .38SPL was generally thought of as better than the 9mm Luger, because the 9mm only had FMJ bullets, unless you handloaded.
Back then, the .380 was thought to be the absolute bottom level minimum for defensive use, by those who were "serious". Then the 9mm, then the .38 SPL, .45, and .357. Generally (there were, of course a lot of differing opinions).
Today, with modern factory ammo defensive loads, the line is much more blurred (and we still have a lot of differing opinions).
If you think the .380 is a better choice for you, then its a better choice, for you. I wouldn't choose a .380 over a .38 because of the caliber, but might choose one (or a .32acp) because of the gun, in a given situation.