Depending on what kind of website you are hosting the choice between KVM vs. OpenVZ can make a difference. Most KVM VPS plans cost a little more than OpenVZ. OpenVZ plans are often cheaper when compared to KVM plans. The main difference between OpenVZ and KVM is that KVM resources are isolated. If a web host says you are getting 1024 MB (1 GB) of RAM than you will have that RAM for yourself. While with OpenVZ your memory can be oversold without you knowing.
With KVM you can install FreeBSD, NetBSD, *BSD, or Windows. While with OpenVZ you choices are limited to only Linux distributions.
-Supports more operating systems (FreeBSD, Windows)
-You can change kernels
-Resources are isolated
-Swap memory is supported
-More overhead because each VPS has to have it’s own kernel
-Often cost less when compared to KVM plans
-Uses a shared kernel results in lower overhead
-Faster and more efficient
-Burst RAM is supported
-Web host can oversell resources
-Your VPS relies upon the host node’s kernel
-Swap memory is not supported
-Other VPS users can borrow your unused memory if you ain’t using them