Author here. I ordered them based on time of publication, and evaluated them based on the contents of the paper. My summary wasn't meant to be a substitute for actually reading the papers either, the Borg paper states that it started out as a centralized scheduler and has evolved over time, and also that it's been in production for over a decade. Clearly, it predates Mesos and Omega.

I've heard varied things about the use of Omega in production. The Borg paper mentions that it runs 98% of machines at Google, but that number is apparently dated. One person said that Omega runs all the batch work, and is being rolled out further. However, I've also heard it's being phased out.