Both were excellent series. DS9 had better continuity and character development, but I think TNG had over DS9 a superior enemy. The Dominion rocked, but the Borg were near invincible! Picard and co. were lucky to defeat them. The Dominion showed little sign of being technologically superior to the Federation, and the Federation even managed to counteract their polaron beams.
The arc with the Prophets was never properly explained - were they transfigured Bajorans from the future? Did they create Bajorans and long ago tell them to worship them?
There were too many open questions there. And why did they choose Sisko as their Emmisary? Why him, from trillions around the galaxy? Why not a Klingon from Qo'nos, or a Cardassian, or a Tzenkethi or a Talarian, or a Romulan?