If I said Trisquel was the best distribution it was probably in relation to
its broadest appeal and ease of use as far as free software distributions go.
I wouldn't necessarily recommend it for all users.
As others are saying it's relatively stable, it's compatibility is excellent
(has the same patches applied as Ubuntu, but to linux-libre kernel), has a
sane user interface, is well supported (ie the best, see
libre.thinkpenguin.com, every component/system supports Trisquel or will "out
of the box"), etc.
Comparatively it has advantages over Ubuntu in that you can be confident that
the hardware you buy will continue working. When your dependent on non-free
components your dependent on the companies in control of those components for
security updates, fixes, feature improvements, and updates that make it
compatible with the current kernels, etc.
There is a lot of hardware out there which we have no control over as far as
support goes. If we want to change that we need to move away from it and not
towards it. It's not just a hardware thing.
There are lots of examples where users have been hurt: Adobe discontinued
flash support for non-Chrome browsers, Oracle retracted its non-free license
such that distributions couldn't bundle the version of Java that most
companies test again/write for, etc. All of these things have had a major
negative impact on users. While many people here didn't run into that problem
because they chose not to use sites/non-free components more people need to
take that stance for it to make positive difference.
