The short answer is, it depends on what lighting system you are using. Probably their biggest downside is cost, depending on how many pods you want to run. I have used the MLC on & off over the years. On my nano it was great but when I upgraded to a 50 gal I did a RapidLed retrofit using the StormX controller which has a moon cycle function and thus I had no need for the DA moonlight system.
Now I have a 180 gal and I'm using AI Hydra 52's which recommend at least 5% intensity for the moon cycle - that is way too bright for my tank half the time. The other problem is that on a dim moon, when the night cycle ends the intensity immediately jumps to 5% and it's very annoying. As a result of that, I'm resorting back to the MLC in the next week or two. I think it's going to be nice to have the moonlights on independent ramp and intensity schedules with the ability of a little overlap at dusk/dawn.