Chicago is brilliant, but ACL is superior in my book (and in terms of staging and his ability to use all the tools of musical theatre to tell a story and create an electrifying production, Bennett is superior to Fosse as well IMO -- I might rate Fosse higher than Bennett as simply a pure dance choreographer). ACL was and remains a complete original, unlike anything ever seen on stage and is the single most ingenious and seemless blending book, lyrics, music, performance, design and staging ever created -- it's impossible to separate any one element from the integrated whole..... and each element was superb and perfectly complimented the others.
ACL also dealt with themes and issues that no musical before had so frankly and has an emotional pull that few other shows can match. While it's also very funny, those dancers' personal stories often have a deep and profound impact on audiences. People identify with many of those dancers on the line -- their fears, their problems, their confessions about their childhoods (how many times did Paul's monologue cause people to weep in empathy?). Whereas, CHICAGO's cynicism and satirical nature, while engaging and entertaining, has something of a distancing effect -- audiences don't connect as deeply with its characters as they do with the ones in ACL.
CHICAGO is great, but merely the finest example of the sort of presentational concept musical that Prince had begun a decade before with CABARET. While its story isn't original (based on a previous play and film), its book and score and staging approached perfection and it deservedly is considered one of the finest theatrical works ever created. ACL is all of that, but also a landmark, a true masterpiece that has no antecedent in the history of theatre.
"What a story........ everything but the bloodhounds snappin' at her rear end." -- Birdie
[http://margochanning.broadwayworld.com/]
"The Devil Be Hittin' Me" -- Whitney