Ubuntu 15.10: KVM vs. Xen vs. VirtualBox Virtualization Performance
KVM was faster than Xen at the MAFFT scientific test while VirtualBox 5.0 was nearly twice as slow.
On this Haswell Xeon system, KVM was faster than Xen and VirtualBox.
Xen scored a win past KVM when it came to the GraphicsMagick image resizing test.
There wasn't a huge performance difference in the largely single-threaded Himeno pressure solver.