What's the difference between Velocity and Waterfall?

I’ve recently found out about Velocity and got interested. But… what’s the real difference between Waterfall? Is it better? And what’s the main reason to switch? Will most of bungee plugins work?

I do not really know about the differences. As far as I know its completly written from scratch.
But no, no bungee/Waterfall plugins will work, but some (luckperms) have a Velocity version, too. Furthermore you can find some plugins for Velocity here in the plugins section