Seems like a good option over not having access to a real firearm, e.g., ownership is illegal. Bear mace or pepper spray could be a nightmare indoors.

From US gov't statistics, the average number of actual firearm rounds (that hit) to incapacitate an assailant is 2.5. It's 12 when you take into accouny the average number of misses.

It would be hard to believe that any non-lethal, kinetic round could be equivalent, as you are just causing pain and disorientation. The chemical rounds (pepper spray?) would be a multiplier, but the issue is you don't have anywhere else to go if it isn't enough. You can't escalate, if needed.

A non-lethal option is also the deterrant of simply displaying that you have a firearm and firing a warning shot, if needed.

That being said, just about anything is better than nothing, if it is reliable.