Well, a LTS release is the end of a meta-cycle where Canonicals own software is supposed to be mature and stable. With regard to Unity it shows. In 11.04 and 11.10 it was barely usable and now it works fairly OK.
AFAIK a LTS is based on Debian Testing instead of Unstable, so even more fixes there. The development is also more conservative and more focused on polishing and fixing than on new features.
It all adds up and as a general rule a LTS is definitely better than a non-LTS.