The fashionable thing to say about The Ladykillers is that the Ealing version isn’t that funny either.  (The either is optional depending on whether you found the Coen’s version funny. I’m leaving the either in.) I think that kind of misses the point of The Ladykillers which is in many ways more a thriller than a comedy. Oh, its a thriller about incompetent thieves. But the narrative drive is solely based on whether the heist will be pulled off, and then if they will escape.
The heist gone wrong movie is a sub-genre with very little to recommend it, (Dog Day Afternoon being probably the best exponent). The heist gone right, the escape gone wrong movie is much more fertile. It can be played for horrific purposes, in a film like Resevoir Dogs. For pathos, in Rififi. For exasperated comedy in Quick Change. The Ladykillers sits nervously between all of these, whilst eeking out an essay on class relations or more properly anti-intellectualism. The Professor, in both versions, is presented as the worst kind of intelligensia. Talks too much, prone to hubris and utterly without morality. Both films present themselves as the mastermind meeting their match in the old lady. This is not strictly true. In both versions she never really actively outwits the thieves, they are unlucky, destroyed by themselves.
The Coens realise that the films is about this battle between down-home simplicity and morality versus the perversion of over-education. It is a pity they do, because it is a pretty unpleasant message to have at the heart of their film. They stress it by having the money finally donated to Bob Jones University, a real Christian university which “stands without apology for the old-time religion and the absolute authority of the Bible”. This is contrasted with the Professor’s education, stressed to be in the Sorbonne – a heathen European institution.
There is much to admire in both versions of The Ladykillers, this theme is not one. The final downfall of both Professor’s come ou of a battle with the intellectually derided characters (One Round in Mackendrick’s, Lump in the coarser in every way Coen’s version). Again we contrast the good heart of the simple folk, with the evil of the intelligensia. The 1955 version may have been contrasting the working class with those which were slowly being pumped out of the enlarged University system. The Coen’s take their contrast from the black south. Perhaps the real difference between the films, which perhaps allows the Coen’s to slightly get away with this is that their film, unlike Mackendrick’s, is not aimed at the group it champions.