Been running Hydros for over 2 years now. I have a Control X4, X2, XS, and two XP8s. I use everything to power my tank except the X2. The X2 is used for my mixing station. It runs a TDS meter (feature that other companies don't offer), water solenoid, & leak sensor. You can expand Hydros to do autowater changes as well which provides the only true end to end automation from monitoring the creation of RODI water to automating the water change.
Ease of use can't be stressed enough as it can handle from simple to very complex processes with a more powerful front end that doesn't require you to use computer coding. The fact that they're built end to end in the US in one lab helps with quality control using higher grade raw materials (i.e. meanwell power supplies for their XP8 module, colored coded BNC connectors to securely connect cables (just liked used in the Airlines industry) to the module as well as help point to which port to connect to based on color, IP65 rated to handle incidental splashes as we're near water, etc) . There's "meat" to these products where it doesn't feel like a cheap plastic toy. Its all about easy of use so that you spend less time coding and more time enjoying your tank. I think we can all sign up for that.
As for accuracy, Hydros is all about making high quality products to meet standards we expect. Look at the new salinity (conductivity) concept they introduced to the market. The industry used the K1 probes which are predominantly meant for fresh water. The salinity aspect was on the outside range of that probe which leads to less accurate results. Hydros, instead, is using K10 probes which are meant for saltwater. They went a step further with the Hydros iV to isolate the testing of salinity so that equipment such as pumps don't potentially skew the results with any stray voltage. Its things like this that they pay attention to which give us a peace of mind.
You should also check out Hydros' free alkalinity testing that is built into the software (you don't have to buy any other add on). It allows you to either use the supplied dosers on the X10 module OR you can use your own high precision dosers to run the Alk tests, Further, they realize that Alkalinity testing has not standardized in the hobby among ALK testers. Because of this, Hydros added the ability so that if you prefer a certain manual titration company's Alk test, you can replicate the results. Ever notice why some autotesters simply are not spot on to your manual tests? It's because ALK is measured with different methods that have different end points (i.e. 4.5 vs 4.2). Hydros allows for that flexibility never before seen in the hobby. Not to mention, they offer offsets as well.
With the X10 already out and the Kraken coming soon, future is bright. Kraken is particularly great as its a WHOLE system battery backup, not just a few pumps.
When it comes to redundancy, Hydros' module ecosystem provides each module you add a FULL copy of your controller settings so that if one module were to fail for whatever reason, the Hydros system continues on with the brain then assigning to the next module to carry the load. With competitors, if the brain goes, your WHOLE system is down, not the case with Hydros.
Lastly, Hydros works with more 3rd party equipment than anyone else (whether through cloud data like autotester readings to carry on dynamic dosing schedules, using 0-10v control for pumps, lights etc, to direct cable integration to work with modules like Wave Engine, etc), but is always looking to add companies as they realize people have different needs and use different branded equipment. We have too many "walled" garden app solutions where they want you to use just their brand specific equipment, but that rarely works for most people. Where Hydros DOESN'T have direct access to these walled gardens, you can still use generic functions (i.e. such as on/off pumps for feed modes/water changes, lighting schedules, timers, and other advanced settings) which will limit your need to manage other apps.
