=== crun-vm ===
Although crun-vm states it let's you "run VMs as easily as you run containers" AFAIK it requires specialised VM images or bootable containers images be created first. By contrast, RunCVM aims to boot any standard OCI container image (as well as specialised container images) and this may make the learning curve and migration path to RunCVM easier for some applications.
=== krunvm ===
krunvm appears much more similar to RunCVM in its approach. However, RunCVM deploys each VM inside a standard runc container, providing an additional layer of isolation and encapsulation on the host (and I'm not sure krunvm does this). Remove the standard container using `docker rm` and you tear down the VM too.
And while krunvm states it "supports mounting additional local directories into the microVM and exposing ports from the guest to the host (and the networks connected to it)" RunCVM does this too, but also makes it trivial to transparently create, prepopulate and mount virtual VM disks within the VM where additional read/write performance is needed (compared to virtiofs that both RunCVM and krunvm use for booting the VM's rootfs).
Both RunCVM and krunvm appear to provide seamless networking experience.
RunCVM gives you full control over the choice of kernel the VM boots, so it can boot what are essentially stock alpine, ubuntu, debian, or oracle kernels. It can even boot an OpenWRT kernel. Or any custom kernel (with minimal config requirements). AFAIK kruncvm does not offer this.
Bootable Container Images are a standard for launching VMs from OCI images: https://containers.github.io/bootable/
crun-vm (https://github.com/containers/crun-vm) is similar to RunCVM in that it can launch container images (or VM disk images) in VMs. It's an OCI runtime so it fits into the podman, Docker, or Kubernetes model.
krunvm (https://github.com/containers/krunvm) is a standalone tool with a similar workflow where you can launch a VM from an OCI image. It predates Bootable Container Images, so I think it injects its own kernel.