which virtualization technology VM do you like provide?

Some people say Xen is more stable than KVM,but from my production server exprience, KVM even Openvz is more stable than Xen.

Because of Xen's Dom0 and DomX,you can't analyze your server's status easily,your only tool is xentop.

another problem is the number of VM host.I use a 72GB server as Xen virtualization server.Everytime xen VMs up to 60+,you can't create any more VM,some strange problem happens. But other KVM server,total VM number can up to 90+ and runs also very stable.

I will never use Xen any more.KVM seems be a good virtualization technology.