DS9, primarily because of the over-arching storylines. TNG started this, where some characters re-appeared more than once (Q, Hugh, Dr. Soong, Lore, Tomalak, etc.). However, DS9 worked better because it was on a space station that was fixed in one place. The presence of the Defiant finally allowed for the characters to get around, since the Runabouts were too weak to take on any real threats.