It’s worth noting that the original Cook’s Illustrated article on imitation vanilla drew a distinction between high and low quality imitation vanilla, and stressed that you should go for the good stuff. But that raises the question: what’s the difference? Primarily, in the types of vanillin the extract includes.
There are types? Yes, there are. For there are several chemical routes to vanillin from the source material of guaiacol. The easier and less expensive of these routes produces a molecule called methyl vanillin, while the more involved and expensive one produces a molecule called ethyl vanillin. You might have guessed already that ethyl vanillin is the stuff you want, for indeed it gives you a more pronounced vanilla flavor.