The whole idea of UV units is to mimic sunlight, the same thing that leads to the formation of some of the sulfur and nitrogen oxides in our atmosphere.
That is not the only factor as I believe I pointed out earlier. Frequency is also a factor as is the tube design.
As for Plasmafire, I had never heard of them before. So I looked them up and again there is really no detailed information on how they are generating the ozone, other than saying something about electrostatic based on Tesla's work. Another site also mentions that they use electrostatic. I have never looked in to electrostatic plasma formation so I can not tell you much about it.