I like .380 pistols for a variety of reasons and prefer them to the 5-shot .38 Special for what they are. However, while I'm not tyring to start an endess ballistic argument, there is no question that the .38 Special has somewhat superior terminal performance to the .380 in the FBI test protocol.
For starters, there are no "FBI expansion standards". None. The FBI only has penetration standards, being 12" minimum and 18" desirable maximum. Within that range, bullets are compared according to final expanded diameter. "Temporary wound cavity" is not a considered factor in FBI terminal ballistic testing of handgun rounds.
There are a slew of standard pressure 38 Special rounds that will easily make those penetration standards: 158-200 grain RNL or SWC, 148 grain WC target loads, 130 grain FMJ, Hornady 158 XTP, and others. The later actually expands out of a 2" barrel. All non-+P.
.380 ACP loads... most of the JHP rounds will not get to 12". 95 grain FMJ generally will, and some selectively chosen hollowpoint rounds will just make it (Federal 90 grain HS and Hornady 90 grain XTP come to mind, there are a few others, but also some spectacular duds).
If you added .38 Special +P rounds to the comparison, there is no comparison. Many of those LHP or JHP +P rounds will make the penetration standards and expand, and hit with a heavier bullet at greater energy than any .380 ACP.
You may or may not think the FBI standards are relevant - and of course that is an all-weekend argument - but considering only those standards, the .38 Special in actual testing is superior to the .380 ACP. Again, I prefer the .380 ACP pistol as a CCW firearm with preferred loads, but the .38 Special is a measurably better cartridge, even in a 2" gun. Out of a 3-4" barrel and/or +P ammo, there is nothing to even compare, the .38 Special is superior.