No problem, B's a girl!
The demo is 4 years old and left up just for legacy's sake. It doesn't represent our current vision and is not at all canon anymore, but some people certainly find it more enjoyable than the prologue due to its emphasis on interactivity and visuals.
The prologue is usually recommended as it's canon and a lot more similar to the full game in style, making it a much better indicator of whether or not you'll enjoy the final product.
That said, the full game will be sort of like a mixture of both.