For me, it's Alien. Great art, sound, callouts, lots of shots...I think it oozes atmosphere and is a great representation of the the theme. The modes I played seemed well thought out and creative. The games weren't set up great at TPF, but it seems like a game that once it's dialed in would play brutal and fast.
Houdini is really early in its life. I think it has one of the coolest events in pinball I've ever seen. The upkicker to wire form to catapult to the chest, then catapult to another wire form is crazy. There is so much space and hardware dedicated to that one sequence though. To me it seems like a one trick pony...but it is early in its development. It has a lot of shots, but perhaps a litttle too crowded in. I hated the art. The other major toy is the theater and it didn't seem to do a lot yet. It could turn into a good game. I thought it felt really solid.