For me DS9 is the best Star Trek series. It's hard to admit since I adore TNG but overall DS9 is better. A few characters in TNG become main characters in DS9. You don't necessarily need the history but it may seem odd watching DS9 and then TNG. As some of these DS9 characters play a much smaller part in TNG.

DS9 was the better television series. But TNG was the better Star Trek.

TNG was far more thought provoking and one could ponder each episode - I'm still pondering some. Other than Sisko's decisions in the latter seasons, what years-to-ponder dilemmas were explored in DS9?

I actually felt that Sisko became a villian at some point, I wish that DS9 would have explored that.