As a substitute for the weapon you mentioned or for a weapon with the stated function of 'coach defense'? I wouldn't probably make a suggestiion for a substitute for the weapon, these types of weapons just don't have any interest for me. I'm not involved in close quarter hostage rescue scenarios, if I want to play that game I go to the paint ball range. As for something just to spray a lot of lead, I have a couple pieces of vintage make and model that can acomplish that just fine. For coach protection I'd choose a little number called the "Thunder Five"
http://www.thunder5.com/docs1.html
This is I believe the ideal weapon for close quarters for women and others who may not have a lot of time in at the range, it also has the added advantage that you don't neccessarily have to see what you are shooting at clearly, like snakes in the grass or night intruders into your coach.