Just finished the Imperial questline! It was amazing and I reccommend it to anybody who hasn't chosen a side yet. I don't know anything about the other questline for the Stormcloaks, but I don't think it could be any better than the Imperial one!
The best part was, I managed to get 2 Daedric Swords out of it, both with powerful enchantments. It's well worth a go at it!