For me to call one of these better than other would be a disservice to...the other. They are brilliant stories of love and loneliness. The setting and score are both perfectly blended together. The biggest difference for me is what may have been lost in translation in, "Let the Right One In". I was still able to catch the emotion of the film. Its rare that a "re-imagining" can live up to its original counterpart but "Let Me In" does so flawlessly.
We are not told anything of back story of the little girl vampire in the movie. It almost seems like she doesn't remember being a human. She just knows that she's been 12 for a "long time". In many ways this really isn't a horror movie. Its a love story and should be watched as such. Not only are these a favorite horror movie, they're also a favorite movie of all time. I probably should have given this movie a synopsis because if you haven't seen it you won't quite understand what I'm getting at. If I have ever stressed that someone watch one of my favorite horror movies this is the one to start with. Make sure you see them both. Oh and watch them with a friend. It's a movie that will remind how important they are.