We offer both OpenVZ and KVM based virtualization. Both have their own benefits.
OpenVZ Pros: VPS can be upgraded or downgraded instantly without any data loss or downtime. They can be easily backed up, cloned and moved across different servers. They come with a control panel with a file-manager to upload files.
OpenVZ Cons: Don't have their own kernel, less software compatibility. Cannot change clock. Cannot manage or install Windows updates yourself.
KVM Pros: have their own kernel, better software compatibility. Adjust clock, manage windows updates, similar to physical dedicated server. Can mount CDROM drive image and install OS from loaded ISO. Direct console access via VNC connection.
KVM Cons: slightly more expensive due to windows licensing. Upgrades require VPS reboots. Hard drives cannot be downgraded without OS reload. Hard drive upgrades require disk partitioning and 15 minutes downtime. No filemanager currently in the VPS control panel.