I can think of these:
- Trisquel doesn't promote the use of non-free software; Debian does.
- Ubuntu-based distributions, such as Trisquel, are more widely supported in
the non-free world due to its popularity and widespread adoption. It's worth
to note that .deb packages are not always compatible between both
distributions.
- There are more pre-built packages in Ubuntu (also Trisquel) than what
Debian can offer.
- Launchpad, a proprietary service, offers additional way to get more
software.
- Debian releases are usually less up-to-date, but more stable (the strongest
point in favor of Debian IMHO).
I personally think that Debian (incl. spin-offs like gNewSense) is the second
best general purpose GNU/Linux distribution after Trisquel, as it is well
supported on non-x86 hardware, such as some low-cost ARM boards and
Chromebooks, or MIPS-based computers from Lemote, and the others.
I've never used Debian before (only tried gNewSense), so take these points
with a grain of salt.
