I enjoyed them both. As a student of theology I particularly enjoy their fictional take on things, that has been fun and interesting to look at.
Anyways, I was very excited for the new Assassin's Creed: Brotherhood when I first heard about it. When I heard they were adding multi player and then I heard the concept for it, I was very intrigued. It sounds like the perfect idea.
Maybe in my head I imagined it to be more than I should have, because I saw some MP game play and it just didn't look like what I thought it would be, if that makes sense.
At the same time I know it's an early build and there is still work to do, but it looked boring and clunky. So much potential that just seems unrealized.
I'll check out some more footage before I make a final decision, and either way I'll probably still get it because I know I'll like the single player.