Depending on what room type you book and possible upgrades Palais Imperial offers more upgrade options. I would probably book a junior suite in Palais Imperial again with hope for Prestige suite upgrade.
After some gentle nudging via email in advance, that's exactly what I got ^ The website had no availability for suites (it's Easter and the hotel is full) but somehow they managed to pull one out of the hat. Full review in due course (though largely similar to yours).