Self-hosted POD: what server should I chose?

The website has a list of open-source servers, but does not provide guidance about how to chose which one is the best for one’s needs…
Having a list of strengths and weaknesses of each implementation would be nice, or a kind of “feature table” comparing them…

Also, I am curious if it is possible/easy to migrate from one server implementation to another (while keeping my data, obviously!).

I adopt CSS (Community Solid Server) as my self-hosted Solid server. Since I am not familiar with JavaScript or PHP. So any one of them is nearly the same to me.
As far as my understanding goes, CSS is relative up-to-date. That’s why I use it. Based-on my practice, CSS is quite user-friendly and robust for a Solid newbie like me.

CSS is the wave of the future. Its modular design is quite robust. At the moment though, many apps are geared for NSS and may not work completely on CSS. That is likely to change in the future, but if your goal is to have working apps rather than play with the sever, you may be better off with NSS at the moment because almost all apps work on it.