in simple way
dota= u start fresh character, lv up by killing n pwning n farming. buy stuffs from the gold u earn, makes u more geng... after this match is over... means over. no part 2 or continue ur char in another game. go play all over again. kill.. farm... pwn... buy stuff.. over... kill... farm.. buy stuff... bla bla bla...~~

wow= u pay to buy the original wow, register up, start to play ur char.. level up by killing monsters n do quest. save up the gold u've earned for mounts (spend gold in AH b4 u hit max lv is not a smart move, no point gearing up) then when u r tired.. off the game n come back later to continue. then u explore the world of azeroth n eastern kingdoms, make ur way to outland (northend too! very soon!) after hitting max lv, u go for heroic dungeons or raids where u join a grp consist of 10-25people or even 40people for pre-bc to kill just bosses where drop epics.

pros about wow compared to dota: u get to keep what u've worked for, dota u lv up but after this round, u start lv 1 again, but u get to keep it for wow. walking around exploring the 'world', just chill n relax n chat with random guys. got more but cant think of any...

cons: u've got to pay for it. very very addictive sial but since if u addicted to dota too... then no difference la. lots of farming. materials... reputations... honor... arena... omg >.<~~ give u 48hours a day maybe not enough also.

the rest all maybe same... the game is srs business, whine n make drama n u r usually out... got noobs n pros in games... but sometimes more noobs that makes ur vein all pop out on ur head.

maybe u got confused from the characters in Dota n WoW. That is if you dont know about WoW's lore. go read about wow's story... quite nice u know... or just play warcraft.

tats all i can say about wow atm...

uhh.. they got a figure of 10-12mill of subcribers because they can count thru accounts that ppl made... but dota is free leh.. not everyone is playing WoW in msia.. maybe 70-80% or more plays dota more than wow? not sure of other country tho... but i think dota 100% got more players.. cant count got how many cuz they dont register or anything to play it. go every cc in msia... maybe 8/10 all dota de... gila wan. sometimes if i go cc play.. im the only 1 playing wow, others playing dota.. can hear them shout n curse like gila... lolz