I have heard that #9 is abrasive, however It does do a fantastic job of removing little minor swirls and microsctraches in the paint. I have never had experience with it, but my uncle has used it on his burgandy 99 yota and did a fantastic job of removing the imperfections in the paint.
The #7 I do use and love it. This is what I will stick with followed up with the #26 Yellow wax. The #7 is not abrasive but I do beilieve it has fillers in it to help cover up the the swirls and sctraches. Hope this helps for ya