Let see if I can help you to make a decision:
If you like simplicity I think dragora is a good choice. It behaves like
Slackware just as onpon4 said; let me elaborate on that:
-Dragora is meant to be the user who makes all the packages so be prepared
for compiling and configuring because it is a slow process.
-It shares similarities with the Slackware way of configurating the system;
simple, and yet elegant scripts, that makes the user confortable in
configurating your OS. It is easy to see and understand the source code of
those scripts to see what are they doing and manipulate those files by hand
if you don't like to use little programs to configure the system.
-The project seems very young but I can asure you that it's improving very
fast.
-The documentation is not very abundant but are very well written.
-They do not use systemd or sysvinit but runit... be prepared for that.
-The installation process is very similar to Slackware.
-They do not mention how to compile with other mechanisms like cmake so I
suggest you to consult (Do not use Slackware scripts in Dragora) in some
Slackbuilds templates. The web page is:
http://slackbuilds.org/templates/
-I want to make clear that even if Dragora shares some of the Slackware
ideas, Dragora is not based in any other distro.
Parabola is also based on simplicity but the Package manager (pacman) have
dependency resolution.
The documentation in Parabola is very abundant do you won't have problems.
The project is basically Archlinux with only free as in freedom packages so
the documentation for Arch is the same for Parabola.
I want to make clear that parabola is a rolling realease with all the pros
and cpons it suposes (sacrificing stability for having the latest packages
available).
Trisquel on the other hand, does not have the simplicity in mind, they want
to be easy to use for everyone. You must have in mind that this idea doesn't
mean to make a less elegant system for more people to use it... let me
elaborate a little more:
-Trisquel is not only an ubuntu without the nonfree stuff. It have more than
100 customized packages, it's own repository, packages from others distros as
well and many other unique features that makes it different from the others.
-Its package management is the same as Debian's so the quality is evident.
-The development is active and the comunity is very dedicated to freedom so
you should be confortable if you care for the ideology.
-The documentation does not seem abundant but you must be aware that you can
use the Debian and Ubuntu ones.
-I must say that is harder to make your own packages in Debian based distros
but you install packages from Debian and Ubuntu in Trisquel if you need it.
Well, I don't know if I helped you in making a decision but I tried my best.
Untill next time.
