What fails to be mentioned many times when asking a question such as this thread, is the variety of T-5 fixtures.
Notice many of those, {not all mind you}, bulbs in that thread are over driven. Plus some of the fixtures are top end units. Thats a lot of difference when comparing what they will grow and depth penetration.
My 6 bulbs fixture is very good, IMO, but when it was on my 90, I think it may have not been enough for sps corals, except for higher up. But then its half the cost of the other units and with bulbs to boot.
Try explaining that to lowballers when selling a unit like that. Sheez.
Anyways, I would not hesitate to use my unit on a 16in. high tank for sps corals. If I was doing a 24in deep tank and wished to run T-5,s I would use one of the high end fixtures, esp. the models that run the bulbs @ 80w or build my own and use the Icecap do it yourself kits. My friend has a 120g full blown sps tank that and it rivals any halide lit tank I have seen.
In defense of halides though, have a look at some of them in our featured section. Some blow your mind sps tanks there. When I look at my friend Mikes 5ft. tank running his three 250,s both 12K Reeflux and a centered 20k, there is no doubt in my mind thats part of the reason for the nice growth and outstanding colors in all his sps
So this basically says, more than one way to run the tank, just buy the correct product for your own needs.