I have decided to stop speaking sternly to my car audio system when I listen to Unspooled and just dump my comments here.
I will pass on the argument whether Alien is better than The Thing or vice versa. They are both about isolation, invasion by the other and an adversary that is both deadly and effective at hiding. They both deal with the dynamics of people living in close quarters for long periods of time. Paul's argument that the characters are better defined in the Thing and that Alien depends more on the acting ability for characters to come through is weak. The characters are more subtly defined in Alien and the cast of the Thing is heavily populated with character actors playing up to their character vs their role. The casting in the Thing has everything to do with filling a stereotype while Alien is not so obvious.
Also: Sally Hardesty in Texas Chainsaw Massacre (1973) is the first fully defined "final girl" NOT Laurie Strode (Jamie Lee Curtis) in Halloween (1978). And yes you could draw a comparison between TCM and Alien in the way it is constructed but it would be a stretch.