Here is an Infoworld article one of my friends sent that reviews the 4 choices for server automation.
Review: Puppet vs. Chef vs. Ansible vs. Salt
The leading configuration management and orchestration tools take different paths to server automation
Credit: Teerawut Punsorn
The proliferation of virtualization coupled with the increasing power of industry-standard servers and the availability of cloud computing has led to a significant uptick in the number of servers that need to be managed within and without an organization. Where we once made do with racks of physical servers that we could access in the data center down the hall, we now have to manage many more servers that could be spread all over the globe.
I know people who are hard core users of each, so even though the reviews may make you think one is better than the other. There are some who have found that one particular tool works best for them.
This will probably all change over the next year as each add more features.