I don't think OMS sells any high pressure tanks. They do have several nice low pressure (2640 psi) tanks though.
As for Faber versus Worthington - I have a Worthington X7-100 and a Faber F7-120. The Worthington is hot-dip galvanized, whereas the Faber is treated by hot zinc spraying and painted. I believe that hot-dip galvanizing process provides more protection against corrosion, especially in salt water, but the experts at Faber think their process is better. The Faber is a nice looking tank.
The Faber tanks are slightly less buoyant, slightly heavier and slightly taller than the corresponding Worthington cylinders. In my opinion, that trade-off favors the Worthington tanks.
I don't think that any of the differences are that serious, though - except the OMS, which is just not a high-pressure tank.
The reason I bought the Faber is that I got a good deal on a new old stock (1 year old hydro) tank on e-Bay. If the price had been the same, I would have bought another Worthington, but I saved about $100 by buying the Faber instead.