I've heard some say the Blazer shoots cleaner than WWB. I'll have to try and see for myself.
I'm not sure if I'll use the Blazer for my next IDPA match, as it's a Classifier, and I don't know if switching ammo all of the sudden would end up kicking me in the butt.
Then again, it's just a competition.
Like everyone else, I buy what's cheap for practice. WWB usually gets the nod but I also like Am. Eagle, Blazer Aluminum (haven't tried the brass yet) or S&B when I can find it. In 9mm it usually ends up being 115gr. for practice but I carry either 124gr.+P or lately, Corbon DPX in 115gr. +P (EXPENSIVE!).
I've got an MK9 sitting in layaway now so I'm anxious to read your range report on the new Kahr as well.