Hey Steven,
I have a Kessil 350W and I do like it a lot, it will be very different than your T5s and I would acclimate your corals slowly to the new lighting they can be intense at 100% on both channels (burned up my hammer pretty good, but it recovered).
So far i have very good growth and color on any LPS and Zoa that grows under it. As for SPS (specifically acropora) i have some that grow very well under the light and need no acclimation time and others that seem to need more time to adjust to the light. I have also noticed some color shifting in certain SPS, i have had 2 blue montis turn green but as they are now growing the new growth is now more blue again. I have no idea if this is due to the LED lighting or the kessil specifically (if due to the light at all).
For me the lack of dawn dusk settings is a bit of a pain as I do like having a dusk setting. I do turn the lights down once in a while because the blues pop like crazy on this light.
I'd love to see your setup and hear your thoughts with two lights over your tank...what species do you normally keep?