Boards are often ranked based on the popularity of the board and we would rate that quite high in selecting something that's workable, that's going to have answers online, for problems that you're going to run into. Be aware of stability and power issues, and look carefully at Raspberry Pi in comparison to Beaglebone Black in this regard. The power source is a noted challenge in the Raspberry Pi for its reliability. Read this comparison of the two boards.
This is a companion discussion topic for the original entry at https://mender.io/blog/selecting-a-yocto-board