Preserve midtone detail: When you think of beautiful black and white images that you have seen, more likely than not you are thinking of the midtones. This is where skintones and a well-lit subject will fall. In the absence of color, texture becomes the storyteller. Better Black and White applies a contrast curve that brings out this midtone detail in a satisfying way.
Built from 35mm black and white film: What makes black and white beautiful? It's film - the unique contrast properties of different physical film emulsions, and how they are developed and timed. Better Black and white is built from a painstaking recreation of black and white 35mm motion picture film. That's why it looks so good.
Better than a simple desaturation: To get black and white, don't you simply desaturate your video, and maybe add some contrast? If your goal is to recreate security camera footage from a convenience store, maybe. But to create a truly beautiful black and white image, you need the contrast curve of 35mm film.
That's what makes Better Black and White better.