Pixhawk4 Mini and Arducopter -- Bios

I need to flash my new Pixhawk4 mini FC with Arducopter firmware in order to use the Arducopter Antenna Tracker. I noticed there is an option to use either NUTTX or CHiBios. Which works best with this combination? I here the hardware works better with NUTTX bios and Arducopter works better with ChiBios. Does anyone have any input?

Nuttx and ChibiOS are embedded operating systems. The way it is now, PX4 firmware sits on top of the Nuttx operating system, ArduPilot on ChibiOS, so you don’t really have a choice of operating system separate to the choice of firmware.
The PH4-mini hardware itself doesn’t care.
There was a time when ArduPilot could run on either Nuttx or ChibiOS, but we dropped Nuttx support some time ago.

It seems odd that QGC has an option to load either one with a firmware change-over from PX4 Pro to Ardupilot.

Would this affect how the FC reports Mavlink information to an Arducopter Antenna Tracker ground station? That’s the whole reason for loading Arducopter in the first place

I suspect QGC just hasn’t removed that option since ArduPilot dropped Nuttx support. If it actually does load a Nuttx firmware it’ll be two years old. For Copter use a ChibiOS firmware.