But the fmj will always penetrate deeper and in the case of 380 that might be more important than a slightly larger hole.As far as it goes this is likely true however death of the assailant isn't a requirement for successful self defense. Most handgun shootings are not lethal and certainly not immediately lethal. The purpose of using JHP is that it makes a larger hole and if you have to rely on circulatory system depletion to stop the assailants agression then a larger hole brings that on faster.
At best a JHP will expand and produce a large wound cavity, at worst its hollow gets plugged or closed off and fails to expand so it acts as a solid nose bullet. Solids never expand and have no opportunity to produce a larger wound cavity.
There is also the probability that the the fmj will go through and through leaving two holes in an organ, an entry and an exit hole.