Kind of a long explanation here, just wanted to let you guys know in advance. Also, this is just my point of view.
Personally, I, as a player, think both sides should drop their bullplops and join each other to fight the Thalmor, because they're obviously the real problem here. All provinces should realize this, really. I mean, if that fan theory about the Thalmor wanting to drop the sky on Tamriel to achieve CHIM is correct, well... we have a problem there. And everyone suffers from it.
However, I still chose the Stormcloaks, despite being a Khajiit and hating racists. Here's why:
1. First and foremost, the Stormcloaks are pretty much the first people you meet in the game, and they're generally nicer to you in Unbound than the Empire is. I mean, even Hadvar was kind of condescending when I got to Helgen. ("Your kind always seems to find trouble" <- isn't this a little jerkish too?) So it felt like no matter what side I chose, there would be at least some racism towards my character because he's a Khajiit, and for some reason everyone hates the Khajiiti people, so there's that. There's also the matter that that jerk of a captain sentenced you to death for no reason whatsoever. I know the Empire can't take risks, but the Dragonborn was very obviously not with the Stormcloaks, what with being dressed in rags and, in my case, being a Khajiit. If anything, they could have assumed I was a Thalmor spy considering Elsweyr's allegiance in the war. And even if it is because the player was trying to cross the border illegally, who the hell chops illegal immigrants' heads off without even a freaking trial? That was just the Empire being too lazy to actually think properly about what to do to you.
2. Ulfric may be a racist jerk, but I feel that at least a part of him is really fighting for Skyrim's freedom. I mean, no doubt his goal is ultimately the throne, but I feel like he really thinks Skyrim's freedom is being robbed by the Empire and the Thalmor. My main reason for thinking this is what he says if you meet him in Sovngarde, but there's also how Rikke regards him as a good person who chose the wrong side, and his "the reason I fight" speech in Windhelm. Besides, he was never a jerk to my character and always treated him with respect, so there's that. I know that the Talos banishment was only really enforced by the Empire after Ulfric started the rebellion, but still.
3. You may excuse me for saying this, but I think that if the Empire has to surrender to the Thalmor, either because they have no support from the rest of Tamriel or because they simply just can't fight them, then it's time for them to step aside or change. They have been crumbling ever since the Oblivion Crisis and are grasping at straws here. I mean, every province is secceding, they are not controlling Tamriel anymore. Hammerfell is bringing the fight to the Thalmor rather successfully, so I wonder, if every other province actually liked the Empire and effectively helped them in the Great War, would they still have lost? Nobody thinks they're worth the hassle anymore, and frankly, I agree. We see their decadence even in their uniforms, which used to be heavy armor made entirely of steel in the past, as seen in Oblivion, and now it's mostly made of leather; as in, Bethesda is showing with this little detail that they are falling apart. Not every province agreed to be part of the Empire in the first place (Black Marsh, for example), Tiber Septim sort of took them by force. Why would they fight for an Empire they never agreed to be in the first place?
Personally, I think the Empire is too weak, and has no popular support from pretty much any of the provinces. There's no chance, in my humblest opinion, they'll be able to pull Tamriel out of this mess. I can easily see the next TES game being about a huge war going on between pretty much all provinces (separately, each on their own) and the Thalmor, with Tamriel completely engulfed by chaos. It's the only direction I can see this going in, frankly. But I digress.
So yeah, mainly, I think the Empire is now too weak to rule Tamriel and their days of glory have passed. I think they should either step aside or change drastically. The problem with stepping aside is, obviously, who would rule in their place? Each province ruling themselves? This would lead to a lot of problems, of course, such as currency, laws, etc. The second option is trying to change the way the Empire rules by listening to their citizens more instead of kinda charging taxes and saying "so yeah, you're part of the Empire. Good for you. Here, have a Tiber Septim cookie." Maybe if they could find a way to please at least most of the provinces, they would have their support in the war instead of everyone just shrugging and saying "eh, fl*ff them."
The soldiers from other provinces who did fight in the war, especially the Nords, must also feel extremely outraged that their people's sacrifices to push the Thalmor back were for nothing when the Emperor signed the Concordat, so there's also that. It is kinda justified, to be honest. How would you feel if your dad, mom or sibling died in the war trying to push back a tyrannical rule only for the ruler of your country to sign a contract that agrees to give your people's rights up? They do have a point.
4. Imperial soldiers are arrogant. When you find a Stormcloak party on the road, they sorta just greet you and go on their merry way. If you find an Imperial party on the road, however, even if you are an Imperial general, they draw their swords on you and tell you to "stand back, citizen, this is official Imperial business." I'm sorry, but I don't have to take that plops from anyone. It doesn't matter if they're Imperial Soldiers ("oooooooh, watch out everyone, we got badasses over here!"), they can't just treat people like that for WALKING PAST THEM ON A COMPLETELY PUBLIC ROAD.
5. Come on, the Empire did try to chop my head off for no damn reason. They didn't even check who they were executing. They didn't even know my name! Is this the sort of treatment their citizens should expect from them?
6. I almost never hold a grudge, but when I do, it grows to almost irrational proportions. Sadly, because of their actions in Unbound, I've developed a grudge against the Empire. I'm also a rebel at heart, so I would naturally be inclined to join the Stormcloaks, especially after what I've just seen at Helgen.
Well, I think I covered everything. Sorry for the long post, I just thought I should explain my reasons for choosing the Stormcloaks. Whatever side you choose, please consider the Thalmor are the real enemy here, and they're up to no good. That's all.
TL;DR: Stormcloaks FTW.
Lokir might tell you a cool story about it
