Hi ;-)
Its much more difficult than you think.
Light spectrum build by T5 bulbs depend from used gasses and and phosphor layers - newest T5 bulbs used Tri-phosphor coating(like ATI Purple Plus or KZ Fiji Purple - its almost the same bulbs - like ATI Aquablue and AquaMedic Blue Plus)... We have measured them all - and compared together..
If you will see - T5 tubes produce very narrow peaks - with "fat" lower parts - a specially in Actinic range(400-500nm). If you will comapre white and blue t5 bulbs - you will see that they are similar - the difference is additional peak at 570-580nm and above 610-620nm..
Light produced by LED chips looks little different - you can produce "single, narrow peaks" like in T5.. Even if LED are monochromatic - emitted light spectrum is "wider" than T5 peaks..
They arent "full spectrum" light source - but you have to agree, that can "paint" our corals amazing,isnt true? ;-)
With multichannel panels you are able to simulate almost all avalaible light sources - but only when you have possibility to increase/decrease power of every channel in important spectrum range..
I dont think so that using T5 is strongly needed(together with LED panels) if you can adjust power of each channel(in different ranges)..
Combo units are perfect for wide SPS tanks, because T5 bulbs are linear source of light - and they produce "filling light" which allow to cover all dark areas without any shadows...
For example - please compare that two spectrums - one from our Hyperion SMT and second, from other very good and popular lamp.
Our didnt use white leds, the second uses..
Please compare how that spectrum is builded - all lamps are on 100%(as I know)..
You can see MAIN difference in range near 500nm.. How much important it is?
Its VERY important - please take a look for that chart - and notice, that almost 40% from ALL DISCOVERED corals pigments have excitatation(absorption) area near 500nm(485-515nm).
You can believe me or not - but using additional T5 bulbs for better corals colors(nice and stron pigments) is not needed if that area is covered.
Of course - it have to be PROPER light intensity to deliver proper amoutn of energy to Chlorophyll cells and produce food(glucose) for coral by symbiotic algae..
If power will be too small(even if spectrum will be proper) - coral will never be colorfull - it will go brown or will bleach(if algae will die).
Regards
Przemek
PS. I compared that spectrums using founded spectrum charts - with information on which ranges(wavelenghts) they are drawed.. I dont know why the other led spectrum is shifted strongly to left(430-435nm peak) - its not possible with used LED config so maybe its mistake(probably).