Persona is King.  With that out of the way...

Which do you prefer: Final Fantasy or Dragon Quest?

I have always felt that Dragon Quest was always the better product from a gameplay standpoint, and it strived to stay true to its roots while catering to its fan. Final Fantasy has more flair, but I felt it has strayed from its root to appeal more to a mass marketable audience.  And I never thought I'd see the say when Enix and Squaresoft finally merged as one once being direct competitors.  Between the two, my vote is for Dragon Quest.  If Final Fantasy fell off the face of the earth today, I'd feel no big loss.

Never liked the amount of grinding Dragon Quest has.  I mean, it's still insane.  

I love 8...

I much prefer the Dragon Quest over Final Fantasy.

FF > DQ for me by a large margin. DQ8 was great, but the only one that really stands out when I think about the series. FF6 is the greatest game of all time. So, yea.

Dragon Quest is superior and always consistently quality. FF is a mix bag of great to mediocre. I like FF, but DQ is much better. Their worlds feel more alive and have a lot of personality. FF is more for the western audience that like a lot of deep story. DQ is more about world building and helped pioneer many games such as the SMT franchise, Mother, and Pokemon series respectively.

Final Fantasy for sure. One thing that I like about it is that they mainly have voiced protagonists, unlike Dragon Quest where they're silent.

Just know I had to show up. But this is a battle already known. It's going to be Final Fantasy, and rightfully so. I love Final Fantasy as well. But Dragon Quest 8, imo, surpasses Final Fantasy 1-14 in every way possible. To me, it's a perfect game and it's why I love the Dragon Quest series so much. In terms of legacy, Final Fantasy has done so much more for the industry in terms of technology. Dragon Quest laid the groundwork for the console JRPG, and the job system. Both have contributed much to the industry.

I still don't think Persona or SMT comes close to either FF or DQ. I'm gonna have to go with Dragon Quest simply because Dragon Quest 8 was the first game I played that made me understand that games can be experiences, not just something you do to pass the time.

I also think voiced protaginists are overrated. I don't need somebody to speak for me, I like seeing myself as the main character. Othewise, it's like playing an on rails story in terms of my experience. 

FF for me personally though I recognize that DQ is a much more consistently good franchise.

It is personal preference when it comes to the tolerance of the amount of grinding one would allow, but I can see why it's not as much as  an issue in Final Fantasy becoming more and more mainsteeam.