There are many theories regarding ammunition and stopping power. Having no direct experience but after reading too much on the subject
, FMJ rounds do penetrate farther than expanding bullets and can cause damage past the intended target.
The effectiveness of hollow point rounds depends on several different factors - bullet construction and impact velocity among others. The ammo makers are much more advanced in this regard and make bullets that will expand at lower (handgun) velocities, but to be consistently effective in fight-stopping there seems to be a combination of bullet weight, velocity and caliber that works. The .380 is at best borderline in all these respects.