Honestly, I think Hydros is the furthest-reaching ecosystem of them all. More brands work with Hydros than Apex, GHL, or ReefFactory. The only place where they don't have much extra brand support is lighting, but any light with 0-10v control works. Now, with the addition of the Maven (coming soon), there's nothing that anyone else has that Hydros doesn't. You could have purchased the 2 Focustronic devices, or the Kamoer auto-testers, but the general feeling is/was that they were less reliable and more expensive for what they were than the other offerings... But now that Hydros has its own tester coming out, it's kind of a different ball game.I’d love to know this as well. Want to get in to an ecosystem and want as much as possible from one company to not have to many applications for my tank setup.
The question that will come up for most people is, does it work with my chosen other products? Like, if you have and wish to keep VorTech pumps with Mobius, you're likely going to be unable to control them with Hydros (or anything other than Apex really), but if you use Gyres of any brand (as far as I'm aware), or Sicce, or Tunze, you can control them just fine. Same with Return Pumps.
Unfortunately, there is no controller ecosystem that controls everything, so your current combination of hardware will likely dictate which controller you go with unless you're willing to switch some of your equipment over to make them compatible. I've got ReefOctopus VarioS return and skimmer pumps on the list of things to buy so I can switch out my Return and Skimmer pump for something compatible. The best part is, most of the time Hydros saves you by reducing the number of power bricks you need, since their WaveEngine not only controls most of the pumps, it also powers them completely, no other brand has this functionality that I am aware of...
Don't get me wrong. I am far from a CoralVue fan. When I bought my ReefOctopus tank and learned they were in charge of the Warranty, my customer service experience with them was sub-optimal. But if you're looking for something that you can get "as much as possible from one company" so that you "don't have too many applications for your tank setup," that's where the Hydros system shines, honestly.