Just watched Footlight Parade and I stick with my original decision of choosing 42nd Street.
For those who wonder about this discussion, there is a trio of musicals in the early 30s that made quite the "splash." They were produced by Warner Bros., all three had Dick Powell and Ruby Keeler and more importantly Busby Berkley choreographing all three. The songs for all three were written by Harry Warren and Al Dubin. All of them focused on the making of live musical productions, and as a trio they pushed the movie musical into high gear.
42nd Street was the first of the trio, and opened the door to this "backstage to the musical" idea ending in one or many lavish musical numbers. Following it is Gold Diggers of 1933, which was already in production before 42nd Street was released. Footlight Parade was built on the financial success of the first two, and so able to afford bigger musical numbers and a larger cast.
I love the presence of Cagney's acting chops in Footlight, but the greater loss in that film is Ginger Rodgers, who, in my mind, is a comedic wonder. Without her side quips the entertainment of the film was reduced. The male gaze is prevalent in all three films, but in Footlight it seems that they had a premonition that the Hayes Code was going to be a serious concern, so they made the film as risque and "non-PC" as possible, including a scene in an opium den, mentions of prostitution and many "upskirt" shots. Thoughtlessly, of course, they have some racism, colonialism and sexism thrown in. Although the ending numbers were lavish and the final one includes Cagney (a great song and dance man), I couldn't appreciate them because I was wincing too often. Footlight Parade is snappier than the others, music and dance in almost every scene, but Cagney seems to be the only real plus to that film.
Of the trio, I think Gold Diggers is my favorite, with the long but wonderful Remember My Forgotten Man sequence ending the film. Ginger Rodgers at her quipiest and it is just more fun. But I stick with 42nd Street because it was the first and most influential, and it is more recognized by critics and on lists. I think it is remembered better and is the only one of the three I had heard of before I became a movie buff.