The OMS workhorse I'm thinking of is a simple piston first stage--of a different design than the HOG piston--and an unbalanced, non adjustable (without opening the reg up) 2nd stage.
While the OMS Workhorse is a fantastic regulator, it's a very, very different style than the HOG regs. Hose routing is very different, as well.
I use HOG for backgas and stages, OMS Workhorse for deco, and am very happy with each in their respective uses. The routing for the Workhorse wouldn't work as well for my backgas, and I like having my primary 2nd stage externally adjustable, but both of them work just fine.