Richard T. Jameson has an excellent piece up on his blog, Straight Shooting, entitled "also-true 'Grit'". You can (and most definitely should) read it for yourself, but in it he compares the new Coen Brothers film with Henry Hathaway's 1969 original. His conclusion:
So if I had to pick only one True Grit movie to take to the proverbial desert island, it'd be Hathaway's, Wayne's, Ballard's and, while we're at it, Elmer Bernstein's: that gentleman was Wayne's music scorer of choice in the Sixties, and the Bernstein sound laid over one of Lucien Ballard's high-country shots of quivering aspen and immeasurable, clear-air vastness imbues the moment with mystery. (The score of the 2010 version, by regular Coen collaborator Carter Burwell, runs variations on "Leaning on the Everlasting Arms," a folk hymn best known from Night of the Hunter.)There are a few things I find particularly cogent about Jameson's review: his perceptive connecting of the Coens' True Grit to The Night of the Hunter; "What she doesn't know, we don't know..."; and, "The beauty of it is, though, that we don't have to pick one True Grit."
The beauty of it is, though, that we don't have to pick one True Grit. Both are worth having. We take for granted that any Coen picture is going to be a work of impeccable craftsmanship, and yes, Roger Deakins is at the camera once again. The brothers' fidelity to [Charles] Portis' novel not only honors a great literary achievement but also makes for a narrative with fascinating interruptions, digressions and enigmatic encounters - in short, storytelling of a perversity the Coens usually have to generate on their own.
Like the book but unlike the 1969 movie, their True Grit has a narrator, Mattie, and keeps faith with her point of view. What she doesn't know, we don't know.