I am thinking about making an orc berserker, who is obsessed with fighting and honor. He does not care about politics or the attitude, all he cares about is blood, honor, fighting and the safety of the Strongholds.

So yes, any reasons for him to join The Stormcloaks? Because I don't see a big reason for him to join The Legion.

Perhaps by chance, depending on who he speaks with first and learns of the civil wars ongoing nature, he could join simply for the sake of the fight? Obviously if he has honor he isn't killing indiscriminately so he must have goals that could in ways be met by siding with either side.

When asking him what honor means.
He would say: ''Honor means fighting for your believes and the people dieing without reasons.''
Considering Talos is outlawed and his worshippers get killed for worshipping him, he would find that very offensive, which might result in him joining up with The Stormcloaks.

There's a perfectly good reason for him wanting to join the Stormcloaks. Take the beginning for example, you were captured and close to being killed by the Legion ! You got away and now hate them and decide to take revenge on all of them.

How about that ?

Considering he is wise, but hot-headed. That would piss him off quite alot.