One thing in certain, when looking at nginx's results, independently of the distribution, I could see what many people say about it: it's lightening fast!

@Igor Sysoev
I did look, actually. Both webservers started refusing new connections after a certain amount, as I mentioned there. I didn't go on further tweaking because of what Reinis Rozitis said. I changed a couple of standard (and important) settings in every kernel to be the same, as I mentioned, and I increased the open file limit in order to be able to complete the tests. Other than that, I didn't do much since my purpose isn't to squeeze every distribution and see what I get (after all, it would be pretty similar that way... it's all Linux). I just wanted to find a distribution in which I'd go on with my Rails-oriented research.