Not only my opinion, the opinion of major law enforcement agencies like the FBI that do extensive testing and training.
Look, the US military uses FMJ because of The Hague Convention, not round effectiveness.
“Knock down power” is a specious term. No handgun is knocking anyone down.
Round effectiveness is a function of weight, velocity and expansion - all of which combine to create a wound channel that incapacitates the assailant.
The FBI, famously, went to 10mm when 9mm FMJ failed (after several hits) to stop two determined assailants in the 1986 shoot out.
The best trained agents, with the best hits possible given the tactical circumstances, and 9mm FMJ was tragically ineffective.
The 10mm spawned the .40 and police agencies everywhere adopted the .40.
As bullet design changed, modern 9mm hollowpoints perform far better than FMJ, and the 9mm has become the FBIs choice.
Police agencies across the US are going back to the 9mm, for its lower cost, lower recoil, higher capacity, and better officer qualification statistics over the higher recoil .40 or .45.
But all of that is enabled solely because 9mm hollow point ammo works.
9mm FMJ is still a poor choice for defensive purposes.