I like both series but prefer TNG. It’s the one I grew up with (typically more important in determining which show is someone’s favorite, looking at larger numbers not anecdotal feedback), and it’s the more high-concept and aspirational. Also, DS9 had a chip on its shoulder that for me detracted from what it might have been. You don’t watch DS9 without feeling you’re not at the “cool kids’ table.” You’re with the drama kids. It’s awesome, but there’s baggage. And the melodrama (popular with genre series of the time like Hercules, Xena...and since) seemed like a crutch. I really wish they played it straight. Also, the war arc would have been better if it was less WWII In Space! I forgive early TNG because it was the first new Trek in the modern era or whatever (DS9’s early seasons were structurally better but didn’t have as steep a learning-curve), but late DS9 seemed like it was rushed, stretched, and thematically a step backward. A couple steps, if you count the pah-wraiths and red-eye Dukat. TNG’s last season and a half was weak too, so I’m giving more my critique of DS9 more than my reasons why it’s better/worse here, but these things annoyed me because I expected more from Trek overall by that point.