Houdini does look interesting, I didnt like the pink/purple mess when first released pics, but think its actually a bit worse now with the huge houdini head and lettering - somewhere in the middle would be awsome. The backglass and screen and ramps look awsome. I want to play one, and actually see a vid where you can here the music and sounds would be great.
Aliens looks really great to me, everything fits - sounds are great and layout looks sweet.
Id take aliens, but houdini is looking promising!