I don't think there is too much difference between UV sterilizers. It's mostly a question of sizing the unit. More to the point, do you really need one at all? Bacteria blooms usually go away on their own in a few days. Typically they occur in newly set up tanks.
Installation and flow rate is very important when using UV. You need to give the UV time to kill what your trying to get rid of. Algae doesn't tank much. Bacteria takes a bit more UV. Diseases lik SW ich require quite a lot. You usually want a fairly slow flow rate through the unit. This may mean using a T in the maki pump's return line and valves to send only part of the pump's flow through the UV unit.
I'd expect a bacteria bloom to be cleared up in a day or two at most.
You may have a completely different problem. If it's a new system, this could be fine particulate matter from the live rock or sand.