i played Maplestory longer than Flyff, but if i were to choose between the two of em, i'd pick Flyff. Maplestory and Flyff both have grind, but Flyff has way more character classes with many different builds than Maplestory, a larger world to explore and theres a bit more to do it in than grinding. Maplestory just gets incredibly repeatitive since the only thing you do is grind. if you party in Maplestory, the grind just feels increased and with the insane increase in hackers, its even worse.

i played Maplestory till 8x (gave up 3 times on the game)
don't remember how long i played Flyff for...but all my friends that play it say its way better than Maplestory.

edit: i got this ad right after this post, i lol'd