I’ll start.
For Guinan: I loved that her character was that classic trope of the “bartender / therapist” who was always around, but never got too involved in the main plot. She would give casual advice, but wasn’t officially an “advisor”, so it served the show well for the main characters to share what they were thinking.
For Quark: He was unquestionably the better developed character, with his own wants and desires that frequently intertwined with the main plot. He also served as a sort of foil to the values of the federation, which let the viewers see how greed was incompatible with the best interests of the people.
I love both. Which was your favorite? Which approach did you like better for the “bartender” character?
I got to agree with Steve Shives that Guinan was a better councilor than Deanna Troi.
However, I loved seeing Quark as a character more. I’m some cases, he gives great commentary on hu-mans. In other cases, he is great as someone who gives character to the station; Quark is that bit of shitberg floating on the surface that shows a lot worse is happening underneath. Quark is authenticly fake I love him for it.