Never owned a Metal Zone but played with the original Metal Zone from friends.
Now I have the MT-2W I actually don't understand I never bought a Metal Zone.
I love all kind of Boos distortions, I have the Powestack, Combo Drive, SD-1W, all have their own purpose. Bluesdriver Waza & SD-2 on the Wishlist and maybe the Angry Driver too, love them all.