I bought the OOO version for the first time a couple of months ago. I liked it, but the Activator Serum made my skin sting a little bit - not burn, but a little stinging sensation. The Activating Gel in Philosophy's MD Peel hasn't ever made my skin feel a stinging sensation. The OOO seemed nice and a less expensive alternative, but I'll stick with Phil's MD Peel, since it doesn't cause any issues with my skin.
♥ Life is beauty full ♥