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!
That big difference is the only reason why many people will start investing more in bitcoin.
I am not against Libra coin because it will pave the way for many investors to the world of cryptocurrencies.
This is the only reason I like Libra because it is owned by well known brand which will make it gain traction and hence popularize currencies like BTC and ETH.