I have a 6 bulb ATI powermodule over one of my tanks and it does provide a nice diffuse light. Bulb choice is a very personal choice. Every person who runs T5s will have their own t5 preferences. I think where people should start is figuring out what overal colour temperature they want their display tank to look. That is, onnthe yellower side? (10k), or bluer (20k), or in between (14/15k). Then find the bulbs that will achieve those colours.
For the record I am a halide fan though. Both fixtures will achieve the same results at the end of the day but to me nothing beats that halide shimmer.
