I believe the Imperials are the better faction, it is clear Ulfrics intentions are purely selfish, whereas the Imperials are simply doing their job to maintain the peace, without the Imperials the Thalmor would obliterate Skryim and the Empire would lose a great deal of support in the war, if another great war was to arise, the Empire would most definitely need Skyrim's help to prevail, just in the same sense that Skyrim would need the help of the Empire.
You would think Ulfric would realise that, without the Empires help, Skyrim would be under the control of elven kind, but i suppose his hatred for the elves has blinded him of the truth.