There's 3 versions of Sally's song that were really good I've heard. Amy Lee's version, Fionna Apple, and Now Billies. I liked Fionnas version most until now
It's an annual (except for last year) event. They play Nightmare Before Christmas while the orchestra plays the score live and the original voice cast reprises their roles and sing the song live. So essentially it's a live interpretation of NBC.
Let's not pit up two talented artists against each other. You clearly favor one over the other but that doesn't mean Billie's version is inferior objectively. Both are great in their own ways.