That seems to be a tough question to answer. My first instinct was to say there isn't a meaningful difference since they're both using the same runtime (runc) and have an identical CLI. I hoped maybe the source code for this project would be helpful, but the installer script isn't in the repo, and when I download it to inspect, it's not consistent on its own name, links out to documentation that doesn't exist, and seems to be calling docker subcommands that don't exist, at least not in any version of docker I have.

It appears that docker now offers a "sandbox" subcommand specifically meant for fencing AI agents inside of micro VMs instead of containers at all: https://docs.docker.com/ai/sandboxes/. This is the page the installer script meant to link to but got wrong. If you type docker --help, this doesn't show up as an available subcommand but apparently it is. The documentation says you need Docker Desktop 4.58+, which the installer script is again wrong about, saying you need 4.40+, and it is only available on Mac and Windows, not Linux.

This does sound more or less the same as firecracker, but firecracker only runs on Linux, so I suppose it didn't meet this guy's requirement that he probably uses a Mac.