Stormcloaks- rebelled against the legion for not letting the worshiping of talos which the high elves started by stating hes not o god just a man who did some heroic stuff, the rebelion started in markarth with the slaughtering of talos worshiper.
then Ulfric Stormcloak shouted and blew up the high king and rebellion was born.
Legion- want to keep the old ways of the Nords alive
other then that ive got nothing on them
both sides don't sound appealing to me so if anyone has anything else to add go for it