I'm roleplaying a Wolverine-esque quiet badass Imperial, I decided to flee with the Stormcloak rather than the Imperial at the start, because the guy had been friendly to me on the wagon and I didn't appreciate the Imperials deciding to execute one of their own with no reason (it okay off course because they'd return my body to Cyrodill). Seeing the torture chamber reaffirmed my decision and the fact that the rebel King was going to be excuted without trial.
I used to support the Empire, back in Morrowind and Oblivion, but I feel it's decaying without a good Emperor (or even an Emperor) at the helm. So I'll probably side with Stormcloaks.