I took a Mace/chemical class a few years ago, www.S2Institute.com
. The class instructor, Jay Pace, was first-rate. Mr Pace is a SE Asia combat veteran(2 tours as a USMC Scout-Sniper) & a retired sworn LE officer(Largo Florida).
One of the S2 cadre told our training class he had no effect from OC sprays and that about 2/3 out of a 100 people may not have any reaction to chemical agents.
Many cops and corrections officers avoid foam type agents. The sprayed subject can fling OC foam at you or smear it back on you in a rage. A company called Zarc markets a chemical agent called Vextor that uses a new "micro-spin" system. It looks impressive.
I like Cold Steel's Inferno brand too. It's a mix of OC & black pepper(2%).
I have some Mk III Sabre Red but may replace it soon.
I also never saw any commercial grade(open public) chemical agent rated past 2,000,000 SHU. What brands are around 5,000,000 SHU?