DQ is more about good RPG design, interesting dungeon layouts, novel puzzles, balanced classes and enemies, and a challenge that scales with the story. FF is all about presentation, challenging how games can tell stories and establish gameplay in new and interesting ways. You can see this in FFI which by comparison had flashy battle animations for its time but mechanics and design wise was a mess. FF's best forays into mechanics were V and VI which had some insane dungeons and very deep customization but they were easier to break and the classes not as balanced as DQ. On the other hand DQ5 branched into Square's territory, messing with a lot of narrative techniques and some big shocker moments. DQVIII is the game I recommend people play first because it's so big and beautiful and it's nice to see what your characters are doing in battle, something that superficially kept me away for a while.

I like both series, they have a lot of my favorite games but I've played more DQ as an adult because it has more "steak" behind the sizzle.