The second PDF in the link below compares the Raspberry Pi with the Beaglebone Black for a next gen APM. The nod went the the Beaglebone because of more GPIO, PWM support, and the two PRUs for realtime operation. The Pi B+ helps the first point, but not the other two. There is also a really interesting page in here on the latencies that are required.

BTW, this was written by Andrew Tridgell of Samba fame.

http://diydrones.com/profiles/blogs/a-peek-into-the-future-o...