I don't trust (and don't like) the apex modules for a couple of the things I have (echosmart/maxspect) - their own controllers work far better than trying to control them with apex. My apex is used to monitor and to turn off/on given things for maintenance. If you like your system(and it looks awesome) - why change. Have had 3 tank meltdowns with apex (faulty chips each time) - and won't go back to it controlling lights/pumps, etc on its own). You asked for my opinion - thats it - for the Apex defenders - its not a slam against Neptune - I still use my controller - but the software/controllers that come with the actual product is a backup/failsafe.
I would keep what you have until you have a reason to change. EDIT - the fact that the current modules are no longer made - may be that reason - but Were you to buy an apex - I would tend to run it the same way you are using your current controller.