There are a lot of choices for virtualization.
In many cases for enterprises the choices get complex.
Can you host all of your virtualization environment (ie your cloud) in your own data center.
Will you need the ability to scale temporarily at times beyond your data center.
Will you eventually move to a public cloud provider like Amazon Web Services
AWS.
Some of the Virtualization environments have better management systems than others. Some have none.
If there's any thought of using a public cloud Service Provider then you choice of your internal Virtual environment is critical because to work in a hybrid of public/private cloud you want your virtualization technology to be complimentary or you'll incur extra costs/time convirting from one technology to another all the time.
As part of those choices you also need to decide on a Management platform for your virtualization environment.
You need a tool that helps start, shutdown, migrate, auto-scale, inform you of capacity etc etc.
Hopefully you can find something that works in both your public and private cloud.
