Why is that obvious?
I don't doubt it's obvious to you. But as a die hard lover of both shows, I actually think KOTSW is a better musical, if for no other reason than because it is not based so heavily on cynicism and making a point. KOTSW has characters you care about and a heartbreaking story, on many levels, and also has the darkness and the showbiz metaphors and such too. It's the same reason I put Assassins lower on my Sondheim list than I might - it's a brilliant show I adore and admire, but as a musical it's hard to compete with characters in a story that engages you and excites and moves you. This is why I would probably rank KOTSW over Chicago... though I think about are exceptionally entertaining and thought-provoking musicals with sensational scores and characters.