The diffrence is very simple:
Long version
If you want to have better readability, use Math.floor. But if you want to minimize it, use tilde ~~.
There are a lot of sources on the internet saying Math.floor is faster, but sometimes ~~. I would not recommend you think about speed because it is not going to be noticed when running the code. Maybe in tests etc, but no human can see a diffrence here. What would be faster is to use ~~ for a faster load time.
Short version
~~ is shorter/takes less space. Math.floor improves the readability. Sometimes tilde is faster, sometimes Math.floor is faster, but it is not noticeable.
