If you are running a Linux host (like Ubuntu, Fedora, or Arch) and need Windows 10 for specific apps or testing, KVM + QCOW2 delivers near-bare-metal performance. Unlike VirtualBox, KVM is a Type-1 hypervisor, and QCOW2 is optimized for this environment.
# From VDI (VirtualBox) qemu-img convert -f vdi -O qcow2 Windows10.vdi Windows10.qcow2 windows 10qcow2