^Deep Space 9 has always had a different way about it compared to its counterparts. That's probably why it's my favorite Trek series. It pushes boundaries the other series won't even touch, which makes for great character development and compelling storytelling.
DS9 benefited greatly from following straight from TNG: the latter series presented an extraordinarily optimistic outlook that begged to be explored outside the confines of Starfleet culture. Whereas the strength of the show is often ascribed to the complexity of story telling and depth of the characterizations, the setup, the confrontation of people who were not only of different ethnicities, but also of different organizations, allowed for the greatest exploration of ST values.