What pixhawk to get

Hi,
I’m new to the sub/boat field, but I used to build drones, starting with the APM pre-pixhawk 3dr autopilot and the built a few copters based on pixhawk 1. But that was some time ago and now I’m moving in to the wet side of the world and will build:

  • an autonomous surface vehicle (for shallow water mapping)

  • ROV with tether (for fun, 300m depth)

  • AUV/Glider (1000m depth)

A lot has happen on the autopilot side, should i still try to get the pixhawk2? What about more modern versions? What about the Cube?