1) It is a non-profit that has done things I am happy about.
2) It is kind of a standard which allows the sharing of code and parts very easy.
My money goes to Raspberry Pi because it is good at what it does and I like the company.
http://makezine.com/2015/07/22/with-linux-and-creative-commo...
http://hardware-libre.fr/2014/06/raspberry-vs-banana-hardwar...
(Look at the network benchmark in particular.)
Though it may not be intentional the article seems to have a strong Linux bias.
I want more hardware like this and I always use open source software, but I may not necessarily choose to run Linux. Nothing against it, simply personal preference. I would like to see hardware that can run a variety of kernels.