The qemu-img(1) installed on my system claims that it supports every disk format supported by Virtualbox [0], so I guess the only thing left would be to be able to handle the "machine definition" file.

qemu definitely won't do that out of the box, so, yeah, VirtualBox is better than qemu there. But I bet there's a fancy-pants GUI out there that has an import wizard that will handle that for you.

[0] <https://www.virtualbox.org/manual/topics/storage.html#vdidet...>