I love GHL hardware, but absolutely hate their software. I still have my GHL Doser 2, but it's in a box as I now have Sentia Dosers running both tanks. Their app is pretty good and I don't need to connect it to any controller. I have an apex on my main system, but I never liked the DOS, as I thought is was way too big and overpriced for two dosers. I aslo hate Ecotech software, so the Versa wasn't even on my radar.
I would seriously consider the AquaVitro Sentia Dose, they are completely modular and you only need one primary doser and then you can add secondary dosers later on. The app is pretty good and sends you notifications for low reservoir, etc....
Just to chime in real quick—> I have an Apex as my main controller and have these dosers in use:
Kamoer X1 Pro T
Kamoer Continuous FX
—not in use currently but I have 5 BRS1.1 dosers that I used in my previous display.
If you have the budget and rely on an Apex controller I would suggest the DOS. The amount of control, visual presentation in the app, precise timings, use case flexibility, and to top it off its powered through Aquabus so you don’t use up an ac input— it’s just more useful all around.