The devops training site katacoda.com will be interesting to watch. They spin up and tear down _so_ many VMs, their cloud bill must be monstrous. Firecracker is much leaner, so they would save a lot of cycles by spinning up Firecracker over Kata.
I'm not sure how you can make any of the conclusions anyway, unless you know a lot of seemingly private details about how KataCoda is implemented.