I went right to the college of winter hold and never looked back.

I don't know thing one about the civil war in skyrim.

Should I join the storm cloaks? Legion?

Maybe you guys could make a case for your preferred faction. You're more qualified to speak on the issue than me.

who should I fight for?

Do you want an independent Nord only Skyrim? Or do you favour a united Empire where all races live equally under one law?

Decide for yourself. It'll be more fun that way.

has little impact on the world... so toss a coin. They are mirrors of each other anyhow.

What race is your character?

The Empire. Just because they signed the White Gold Concordat doesn't mean they liked doing so. Many still secretly worship Talos. The higher ups in the Empire know that the peace won't last. Peace is lasting only so long as it is convenient for the Dominion, which won't be very long. When the peace ends, the treaty is gone, and full religious freedom is back. What the Empire needs right now is to be united. Ulfric is failing to see the bigger picture. He only cares for himself. Tearing apart and weakening the Empire only helps the Thalmor. When the peace ends.. implied to be very soon, the Empire is going to need all its strength and all its allies to combat the Dominion if they hope to stand a chance at winning.

Skyrim, for all its pride, cannot stand alone against the Dominion, and even if it could, it's throwing away soldiers it could be using to fight the elves to fight the empire. It's also strongly implied that the Empire could pull troops from elsewhere and crush Ulfric's rebellion, but at the cost of weakening its borders to the Dominion, probably leading to an immediate invasion. To quote Hadvar: "What the Stormcloaks like to forget is that the Empire is the only thing keeping the Dominion out of Skyrim."

While one could argue "but they aren't, there are those Thalmor agents escorting rogue Talos worshippers around Skyrim!" I would counter by saying that Skyrim, on its own, would be immediately invaded by the Dominion. A Stormcloak victory would give the dominion exactly what they want.

One caveat is that one entry in Ulfric's dossier mentions: "A Stormcloak victory is also to be avoided, however, so even indirect aid to the Stormcloaks must be carefully managed." I don't believe this is worry about a Stormcloak led Skyrim, I think this is concern about it happening too soon. Remember, the longer the war wages, the more Imperial and Stormcloak troops die. The Thalmor want the enemy troops to be decimated, they want any victory for either side to be Pyrrhic, which is why you need to act now, before it's too late.

I still maintain that they ultimately prefer a Stormcloak victory. It would isolate Skyrim, the most outspoken Talos worshipers, and literally cut the Empire in half, with High Rock and Cyrodiil being cut off from one another geographically.

The Dominion could easily sweep in and take over Skyrim in the wake of the civil war which wasted the lives of so many Nord troops, giving the Dominion a powerful foothold on the northern end of the Continent. With the Empire cut in half, the Dominion could lead purges of the population like they do in Valenwood, and then wage a pretty nasty land campaign against both Cyrodiil and High Rock. One might Argue that Cyrodiil and High Rock would then converge and crush the Dominion held Skyrim, and it's possible, but other factors need to be taken into account. Firstly, that the Thalmor would probably slaughter the Nords wholesale. Their goal is the destruction of the belief in Talos, and you can't take away belief simply by outlawing worship. Secondly, that the Dominion still holds Valenwood and Elsweyr. Cyrodiil would have a hard time helping High Rock against a Dominion held Skyrim when the Dominion is pushing everything it has at its southern borders.

We have a phrase to describe this situation: Divide and Conquer.

Strategically, the Empire is the only intelligent choice, and Ulfric is a Thalmor tool.

The war with the Thalmor will start again, when it does, Talos worship in those territories will be restored. It was a terrible, but temporary restriction of freedom to ensure the long term freedom and livelihood of the empire and its people as a whole. It's ugly, and I don't like it, but that's often how the real world is as well.. we need to pick the lesser of two evils, or the more desirable of two undesirable situations. Ulfric is a selfish tool that preys on the idealism of his Nord countrymen, while the Empire, even when making tough decisions, is actually looking to actually protect them. Skyrim is an important part of the Empire, and always has been. Tullius sees them as his fellow citizens. He may not understand their culture, but he flatly admits to deeply respecting them. This is particularly evident in the differences in how Tullius and Ulfric speak. Ulfric speaks of battle, and honor, and traditions, while Tullius, more often than not, just wants to stop the violence. He is simply more humane in his campaign.