IMO you can't really oversize a UV. The only downside is more expense and possibly more heat but I don't think you can oversterilize the water for all practical concerns.
The main feature of the amalgam units is the smart ballast. It will notify you if the bulb has reached its end of life or if a short is detected. As someone who does product support, this is awesome. The number of consumers who forget to swap their lamp or who have the lamp go out and don't realize it for months is very high.
There is also the additional aid of troubleshooting if the ballast is bad or the bulb is bad. We get lots of people who report a bulb is bad because it doesn't light up, but their old bulb also didn't light up, so it is really the ballast that is bad and not the new bulb. With the Amalgam units, if the lights on the ballast are on, then it is ok, and you know the lamp is the issue. If the lights on the ballast don't work you know that the ballast is bad.
