After doing some digging, I have changed my tune somewhat. I still think a wide flat nose .380 round is perfectly acceptable for self defense, and even preferable under certain circumstances.
However, I have discovered:
1. Some 380 JHPs (like the Hornady XTP bullet) generally penetrate more and expand less than other bullet designs.
2. Nonetheless, the XTP bullet is considered a high quality and highly accurate bullet.
3. In 2000, law enforcement ammo specialist Dr. Gary Roberts wrote an article called "Terminal Performance of .38 Special & .380 ACP Hollow Point Bullets" in Vol. 4, Issue 3 of Wound Ballistic Review. Bare gel tests were used. The Hornady 90 gr 380 XTP round was found to penetrate 12.5" and expand to 0.45" in diameter over a multi-shot average. I suspect that a 3.5"+ barrel was used, but I don't know. Nor do I know the bullet velocity as I can't find this article anywhere online.
4. In 2003, Dr. Roberts was asked why he recommended FMJ in .380 despite his XTP test finding in the 2000 article. Essentially, the question was: why not crush more tissue with a bullet that penetrates the 12" FBI minimum and at least expands a little? He responded that it was an "old" paper where the research was done prior to routine denim testing. He elaborated that "none of the 380 JHPs we have tested expand when fired through 4 layers of denim."
5. However, Shawn Dodson posted his XTP testing using a 3.8" barrel in 1999. Over a 5-shot average at approximately 1000 fps, he found:
10.9" penetration/0.45" expansion in bare gel
14.2" penetration/0.43" expanson in denim covered gel
6. 4 of the denim shots expanded to an average of 0.45" and penetrated 12.2" to 13.9". One shot passed through 18" of gel and presumably did not expand.
7. So this would appear to contradict Dr. Roberts' explanation for why he does not endorse the XTP. The round actually penetrates further in denim and still expands a little bit most of the time.
8. Shawn Dodson's findings were corroborated by this ScubaOz video using a Sig P238 (2.7" barrel). In it, he shoots a block of bare gel followed by a shot through 4 layers of denim. I am not particularly concerned about the overall penetration length, as I don't know if this gel had been calibrated to spec. I am interested that: 1) both rounds expanded, and 2) the denim shot penetrated 1" farther in the same gel block than the bare gel shot. This confirms Dodson's findings and would again appear to contradict Dr. Roberts's reason for refusing to advocate the XTP over FMJ.
9. Here are a couple more videos showing XTP bullets expanding after passing through denim from short barreled mouseguns.
Bottom line, the main concern about 380 JHPs is that if they expand, then they don't penetrate far enough. Here, because the "controlled" XTP expansion is relatively modest, it penetrates well through bare or denim covered gel. And if it happens to fail to expand through denim, then it penetrates even further thus becoming the equivalent to an FMJ round that Dr. Roberts recommends in the first place.
All of that said, I agree with Dr. Roberts that shooting a snubnose .38 special with loads that reliably penetrate while expanding to 0.55" (or single stack 9mms with loads that reliably penetrate while expanding to 0.60") are highly preferable to shooting .380 XTPs that reliably penetrate while expanding to 0.45". Not to mention the potential reliability difference between a revolver and a .380 mousegun. In other words, I understand why he does not care for the .380 round.
Nonetheless, I purchased an LCP because its size and weight allow me to always have a carry piece on me. So the next question is ammo selection. Here is where I think Dr. Roberts is a tad conservative. Flat nose FMJ are good rounds, but the XTP rounds appear to be better.