well i just got started for FFXI i want to play WoW but i have so much money tied up in FFXI i can't do it just yet.
But with FFXI it is about economy, quests, and getting in party's with friends to go kill shit... Levling is a big deal in the game simply because you have to lvl to do some cool shit. the markets are nuts you can learn cooking, fishing, blacksmithing, goldsmithing, alchamey, and a few others i can't think of off the top of my head. Weapons and armor are just about endless in options once you get to higher lvls... there are several advanced jobs to learn later and expansions and updates happen often. its a hard call if you have the money and time buy both
i am not sure in WoW but in ffxi it is kind of a mix ... you engage then the swings and spells are just based on your delay... and weapon stats... not so much player 1 atack... mob attack... the mob could hit you like 10 times before you swing... but it just depends on the stats of each... i'm probably not explaining it the best but its worth a shot... i know WoW is going to have PvP and I think the only thing FFXI has close to that is ballista