Why do people pay more for KVM or XEN?
I can't understand why people want KVM or XEN better than OpenVZ for Linux server. I think there aren't many people who really need KVM or XEN over OpenVZ.
The only strong point of KVM and XEN over OpenVZ I know is more isolation. But do you really need more isolation? From my personal experience, when people on same node abuses, your vps gets slower no matter if it is KVM or OpenVZ. Also, most providers load commonly used modules such as tap/tun and netfilter/iptables for OpenVZ.
AFAIK, OpenVZ has way much better performance than any other virtualization methods. As long as provider does not oversell (and that is the reason why I stick to famous providers such as buyvm or hostigation), OpenVZ seems to be the best virtualization method for common uses of server.
There was one exception in my case when I wanted to use OpenCV library and needed to load special module for better image processing. But except for those special cases, I can't get why people love KVM or XEN so much.
I believe there should be good reason that I don't know yet. Could someone tell me why?