Houdini is the better game already for me (and my son and wife). I was all pumped to get an Alien, but played several games on it at the show and just didn't like it. The word 'clunky' kept coming to mind and it did play slower than I expected. Houdini is earlier in its development cycle and already seemed more entertaining and I think it might really shine in the end.
Now the pin that caught me off guard because I just figured it would suck, was Aerosmith premium. It was actually a lot of fun and I warmed up to the animations etc after a game or two. I wasn't expecting to like it as much as I did.