I really am insistent about not using 9s for much of anything. I used to use them to load my own spreaders for very, very close rabbit targets and crossers, as my sporting clays comp gun has fixed .020" and .020" chokes. Then I discovered Fiocchi Interceptors and stopped loading them myself. They're probably fine for skeet, but I don't shoot that discipline.
Number 9 shot just sheds energy too quickly for me to be comfortable with it, even on smaller birds like quail and doves. Because of that, 9s almost never pass through a quail or dove. I hunt quail a lot with a close friend who believes in 1 oz. of 9s for quail. I've cleaned, and eaten, his birds shot with 9s and mine shot with 7 1/2s. I almost never bite into a 7 1/2 pellet, but it's common to with the 9s. If nothing else, that reason alone is enough for me to not use them on birds.
I've got three bags of 9s that were given to me a few years ago by a good buddy. I use them to balance my Allison XTB boat when I'm driving it alone and want to run it at high speed. The Allison doesn't seem to care what size the shot is, but having not tried 7 1/2s in it, I can't prove that.
