RoM is definitely more atractive than PW, espcially since it's a bit more western.
However, if you're looking for big questing games, I do suggest you try Perfect World Entertainment's other games. They're ALL very high quality games with large playerbases. Ether Sage Online, Jade Dynasty Online and Battle of Immortals are fun and have a good, huge storyline.
PWE really bullseyed the quest factor of their games. Most of them are fun to read (I read them especially because they're short and help you learn stuff about the game).
But RoM also has a large variety of quests, but I can assure you that you WILL be confused after you change classes. I never got around to getting out of the Steppes because just doing it all over again is tedious and much harder. That's just me, though.