I went with the Hydra 32 simply because my LFS is an AI dealer, but I can say for certain that the fan noise (on mine) is overblown. I can't hear it unless I am standing at the aquarium and ALL of my filtration is off. For reference, I also have a 24x24x18, and I made a post with my settings and PAR readings at various points. My nephew was my scribe so it's a little hard to discern some things, but I can always answer questions.
The AI app isn't the most intuitive, and I wish I could type in the slider value I want for each channel, but you have to sit there and slide it until you hit the mark. That, and there's no 'camera' setting in the app, so if you want whites for photos you need to setup another preset for it and switch it. Also, if you slide up or down with 2 fingers, it will adjust all sliders at once (wish I knew that when I was setting mine up - I just learned that last week unfortunately).
I have a glass top on my tank, and I only notice disco when the top has large drops of condensation. I keep it a little salty on the air side to act as a makeshift diffuser which helps a bit and doesn't seems to affect PAR. Eventually I will get a mesh top and the Disco will be non-existent.
I have not effectively figured out how to use the moonlight setting, and at this point I don't really care anymore. I don't plan on spawning events, so it really doesn't matter in the end for me.
I ended up mounting my light ~8.5" from surface as it got the best PAR blend for me. There is a decent amount of room light bleed if that bothers you, but it doesn't bother my wife or I, and it's actually nice that I don't have to turn the overhead lights on late at night and disturb my wife sleeping in the next room.
One thing you will read is that the AI lights will ship and have a flashing, alternating red/teal light. It is a major cause of bad reviews online, but I spoke with AI about mine and they said all the drivers are updated and checked before shipping. It ended up being that the motherboard came loose during shipping and simply needed re-seated which is a very easy fix.
I covered everything I can think of right now... Let me know if there's anything else.
P.S. I think all of the LED's in this price range+ are excellent and you can't really go wrong with any of them.
