Even with the "pretty much" emphasized, I don't agree with the statement above that if you are justified in spraying someone you are justified in shooting them.
I know it depends on the State, but non-deadly force is ok to the extent it is reasonably believed to be necessary to prevent the other's use of force against you. Deadly force requires a reasonable believe that your life is in danger or that you will be severely injured.
Being slapped around or punched would certainly justify retaliating in kind, and it might well justify spraying or shocking someone. I guess that's up to the jury. But shooting them? I don't think so.
As to the OP, I've been tased and sprayed in training. I didn't like either. I don't carry either. If I did, I'd use the spray. With my luck the incident would take place in the winter and the guy's coat would get in the way of the taser.
Another reason not to have these things is personal. I'd probably use them on the Chihuahua that lives down the road from us. This being Texas, his owner would probably shoot me. Then my kin would go after him etc etc. I hate that dog.