Here's how I will rank the 1940 novelettes. This is a strong category!
1) "The Roads Must Roll", by Heinlein. This is famous for a reason. Engaging story with believable characters (although some tending towards unrealistic perfection a la Doc Smith's protagonists). Predicts urban sprawl.
2) "Blowups Happen", by Heinlein. Makes confident predictions about the hazards of nuclear reactors using sparse available information. Not too terribly wrong! Note that it was amended after the war to be somewhat less wrong, and this version is easier to obtain (I think the original was only published once, in Astounding, Sept 1940). The two versions aren't really meaningfully different from a voting perspective, I think, but the 1940 version would have been crazy to re-publish after the war as it makes claims about uranium availability that every reader would know were wrong.
3) "Farewell to the Master", by Bates. A fine story. I understand that the punchline was revolutionary at the time, although now clichéd. It bears very little resemblance to The Day the Earth Stood Still. Please do not vote for it as though it were the movie. Actually read it. It is a totally different story.
4) "It!" by Sturgeon. Fantasy/Horror. Engaging. Sticks the landing.
5) "Vault of the Beast", by Van Vogt. Pulpy nonsense. Entertaining, but clear nonsense to anyone with an 8th grade education. I'd guess it was a parody, except that, well, it was published in a pulp after all. Seems to have two ideas in it, neither fully developed.