SO NEWB: Platform Questions

Hi all, some questions:

How is PixHawk 2.1 support?

I’m debating which fork to take:

  1. Pixhawk 2.1 with an application board, like a pi, for sensor processing

Is there an advantage to having separate boards for the flight control and applications? It seems this could be more fault tolerant, but I’m just coming up to speed on the architecture.

  1. Navio2 with a pi

From what I gather so far, the pi runs Linux and the flight controller runs as a process and accesses the IO on the Navio2. In the event the entire system goes down for whatever reason, it seems like this could be very bad. Is this a valid fear, in practice?

  1. Snapdragon Flight

The Snapdragon looks pretty neat. Maybe the same fear as the Navio/pi? I read people recommend using an external GPS over the integrated unit. Why is that?

How is the dev experience with the Navio2 vs the Pixhawk route? I would think remoting into the pi or snapdragon would be pretty convenient.

I’m planning a tail sitting quad.

Thanks for your help!