Hi Manuel,
There was a topic some time ago on virt-manager . It was a joint effort by @Rosika and myself. It is here
I have used VirtualBox in Linux, but I find virt-manager fits better into the Linux way of doing things.
The most important thing with a VM is being able to get data in and out of the guest system. I found the ‘shared file’ concept in Virtualbox to be rather awkward. There are better ways of communicating between host and guest systems, and that is why we wrote the above topic.
The guest system in Virt-manager can be any Linux distro, or any BSD, or even Windows.
There is a tutorial on virt-manager here
Regards
Neville