It's faster because we made it fast. What's the difference between migrating a container with network, RAM, CPU and disk state and migrating a VM? IMHO, the difference is that the VM has a massive performance penalty and the container implementation does not.

It's not enough to just migrate the container, you also need to migrate the network and the storage too. That's actually the harder part, IMHO. Everyone forgets about network and storage until it's time to go into production and then it gets hard.