I run my 3 tanks on Hydros and have been very impressed with it so far. It's been remarkably stable and quite easy to use.
I did consider Neptune as well, but I preferred Hydros.
Hydros has a lot going for it. They have far better build quality, much easier to configure, the GX connectors are a very good design choice, they are willing to integrate with 3rd party vendors and all of their modules work as a "collective" or a cluster, adding redundancy.
The Neptune Apex has a huge install base so it's generally easier to find gear second-hand and has some power user options that Hydros doesn't have.
With mostly feature parity those who are already invested in the Neptune ecosystem are unlikely to move to Hydros. Neptune is highly focused on vertical integration, similar to Apple.
Since all hydros modules are controllers, it's hard for them to be price competitive in the long run. Up to you if a distributed system is worth it.
The Maven is going to be expensive, but even at $1200 it's competitive with the Mastertronic, and the Trident (x2) if you factor in the cost of the Apex, as it cannot work without also purchasing an Apex. It's a convenience item, so it's not a high value proposition, regardless.