Here's a detailed article on this topic by CNBC:
cnbc .com/2019/06/18/the-difference-between-bitcoin-and-facebooks-libra.html
In my view, the biggest difference between Facebook's Libra and the Bitcoin is that while Libra is a Stablecoin, Bitcoin is not!
Are you joking or serious when you say Libra is stablecoin and Bitcoin isn't? Have you ever thought that Bitcoin has been a decade in the digital currency industry? What about you? so far as it has yet to launch and it is not yet known when it will happen, nor has the token been purchased yet, so you say stable coin instead of bitcoin, for some years bitcoin has been used for pounds unused. Hope before you post here you think it very well first.