Vantric SystemsTeams often pick an RTOS based on what a past project used, which is a reasonable default but not always the right one. The decision should start with your connectivity and update requirements, not the scheduler itself.
Zephyr has become our default recommendation for new designs that need a modern driver ecosystem and OTA support out of the box. FreeRTOS still wins for extremely constrained parts where every kilobyte of flash matters.
Whatever you choose, budget real engineering time for the board support package. That's where most embedded schedules actually slip.