Good question Spazz, I recently bought some T5 daylights and a T5 aquablue bulbs to run on my 660-009 but decided to stick with the URI Brand
VHO actinics. The T5 aren't hooked up yet because I am waiting for the Oceanic hood which is still on order, and wanting to make the switch all at same time.
All the research I did the concensus is that VHO URI Super Actinics is still the standard which everything else is measured. Your best bet is to stick with the proven bulb which is the
URI Super Actinic VHO and wait on the T5.
There are some who actually prefer the T5 ATI Blues ( not in the majority vs. true actinic ). I think mostly because they look brighter than the T5 True Actinics.