The movie with Julie Andrews is delightful and fun, but rooted in a single interpretation. This necessarily limits your ability to experience the dynamic flavor of a live performance, with different actors bringing different strengths and personalities to the performance. Further, the liturgy of the experience in going to the theater - the sounds, the smells, the fellow audience members - is something that can't be captured by the movie any longer.
While live performances of The Sound of Music are very entertaining, the original will always be best because it is the original, the source material. Live music is fun but the performances will always be judged next to the film, which has gone on to become a classic because of how good it was.
Like Mary Poppins, Julie Andrews made the movie fantastic. Sure, the other cast and scenic choices created a masterpiece but Julie Andrews set the mold with her performance. Nothing compares to her vibrant and beautiful acting. She brings the music alive. The scenery is a lot nicer as well, no matter how "real" a stage designer tries to reproduce the show.
I am a diehard fan of the original "Sound of Music" so I was appalled by Kerry Underwood's rendition. I will be honest, I probably would dislike any new version of the musical due to the beautiful melodic pipes of Julie Andrews that cannot be duplicated. When a work of art is so finely done to the point of excellence and perfection, all others pale in comparison. It would take someone of superior musical talent and acting brilliance to change the minds of "The Sound of Music" connoisseurs like me.