I don't have a stake in the Ruby webserver wars, but the unicorn site has a very good discussion about how it works internally, why it's build as it is, pros & cons etc..
This seems to be missing from most of these project sites, which are often just marketing (look! It's better!!), and therefore not very trustworthy.
From the outside it looks like the biggest differentiator in each generation of ruby servers (and, I guess, db managment systems :) is not that the new is better or worse, but simply that has different trade-offs.
You seem have written one of the very few articles I've seen benchmarking this. I'd love to know more about how Puma compares to Unicorn (especially unicorn configurations mentioned by some in this conversation) and Thin for serving rails on Heroku. Many of the Unicorners pushing their solution don't appear to be aware of Puma and its potential benefits. I'm curious if Puma with MRI has benefits, too. Thanks!