QEMU virtual machine emulator is an advanced cross-platform. I say this because if you've installed QEMU on your system, you will not find anything other than a simple command line interface that can be run locally or remotely. In other words, you can build your own graphical interface to run QEMU. You can use a shell script, a GTK-based interface is complex or Qt, or if you prefer, you can build your own web-based interface using PHP, Python, Ruby or Perl. I mean it really is yours.
Another thing why choose QEMU is a factor dependencies. If you Slackware users, then you do not need anything else to install QEMU on your system. Just download the tarball it, compile, install and you're ready. Just remember one thing in building QEMU, you should run your Slackware init 1 or init 3 (text mode / non-graphic mode) for compiling QEMU is a process that is in desperate need of resources. In my system when I build QEMU on init 4 (graphics mode), the development process always stop after a few minutes because the compiler runs out of memory.
Before you proceed, I suggest you to enable virtualization support on the CPU through the BIOS. Then do not forget to load the KVM module and the AIO in the kernel