What is faster? KVM or VirtualBox? Windows 7 definitely faster in VirtualBox. What about Whonix?
What about graphics? VirtualBox used to be a lot more snappy wrt to multimedia playback. Is this still the case or has changed?
More in-depth graphics comaparisons are expected between the two this year.
However some benchmarks  in that article already show superior results for KVM.
 H.264 Video Encoding, Phong Rendering With Soft-Shadow Mapping
Vbox’s new 3D GPU has very lackluster results and only covers extensions up to OpenGL 2.1