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!
Excerpt from the articles
Further, unlike other stablecoins, Libra will not be pegged to one currency but instead a basket of assets ranging from bank deposits to short-term government securities.
Libracoin will not be just your regular stable coin in the tradition of Tether, it's bringing something to the table that other countries consider dangerous, so they banned Libra Coin, I'm still open to what Libra Coin is bringing to the table but I'm 100% supportive of Bitcoin because it is a store of value.
The said cryptocurrencies have lots of differences, one of those is they're different in terms of their monetary policy, bitcoin is widely known to be a decentralized cryptocurrency, if someone has bitcoin, they are the sole custodian of their BTC and the government can't touch it. Meanwhile, facebook libra is like the traditional currency that is backed by centralized institutions and agencies. Another factor that differs from Facebook libra and BTC is the technology used behind them. BTC is known for using the technology called blockchain that records every transaction anonymously on a public ledger. While libra, also uses blockchain technology or a distributed public ledger to be specific, but the catch is, the blockchain of libra is permissioned which means only group of trusted parties can add every transactions.