Those are not comparable products your listing there. You have type 1 and 2 plus desktop stuff in there.
If your wanting to host VMs at your business then I would throw out type 2s (Full blown OS on machine - then vm software runs on that). This would be Vmware Server, Virtualbox (more desktop use - but is making strives to be run on server, etc) but still type 2.
You left off esxi (vsphere) which is prob your best choice - FREE version, and type 1. Will run on loads of different hardware.
Xen was purchased by Citrix, so not sure why listing them twice?
Player is just desktop, and MS virtual server is OLD.. I think latest version is 2005 r2, does not even support running 64bit guests.
Look into esxi - its FREE! for the small shop without need of fancy stuff like vmotion and HA, etc. http://www.vmware.co...r/overview.html