OC4BAv5 was developed before MSFS was released and has airplane drivers and scripts for the PMDG 737 NGX and PMDG NGXu airplanes to be used with the Prepar3D simulator.
Oi4FS was developed to have ONE main program that works with both Prepar3D and MSFS. It comes with airplane drivers for airplanes that use the G1000 NXi avionics, MS/ASOBO's B747 and B787, Working Title CJ4, Flybywire A320NX. Users of Oi4FS can buy add-on drivers for the AeroSoft CRJ, PMDG 737 for MSFS and Leonardo Maddog MD82 airplanes.
Both OC4BAv5 and Oi4FS are shell or main programs that do airplane configurations and start correct airplane driver as used in the flight simulator. Oi4FS is now making OC4BAv5 obsolete, so I am now only using Oi4FS. Oi4FS has also Autostart functions that will automatically start up the correct airplane driver based on which airplane you fly in Prepar3D or MSFS.
To my big suprise, the existing OCP4NGXu driver that is bundled with OC4BAv5 also works with the newPMDG 737 for MSFS airplane. This will allow OC4BAv5 users to have their Opencockpits hardware modules interfaced to the PMDG 737 for MSFS airplane at no additional cost. Lucky OC4BAv5 owners, bad for me.
Users that has bought the Oi4FS and also have the OC4BAv5 can therefore delete OC4BAv5 and use Oi4FS to make configuration and enable drivers for use with both Prepar3D and the MSFS.
Hope this clarifies things.