So we have different versions of Visual Studio (VS). These are Professional, Premium and Ultimate. We also have Test Professional and Express which we will leave out for simplifying the discussion. Furthermore, this is a VS2012 discussion, not VS2010 or earlier. So moving forward, let's just cover Professional, Premium and Ultimate.

The availability of features is based on the edition that you use. As the name suggests Ultimate has it all, whereas Professional has not. Let's take an look at some examples.

Profiling enables you to determine where in code you are spending most of the time and which methods are most frequently called. This is available in all editions of Visual Studio and is a very useful feature for aiding to improve the performance and some aspects of understanding of your applications.

Code Coverage enables you to determine which parts of code have been covered and which not, as well as percentage covered etc. during the execution of unit tests. This provides a valuable insight into where you should consider writing new unit tests. This is available in both Premium and Ultimate, but not Professional. 

In my personal opinion, IntelliTrace is a huge time saver. It enables you a DVR like experience as a developer. So as you debug, you can step back. Furthermore, IntelliTrace logs can be captured from Test or Production or any other environment and can potentially save a month or more of developer activity per year. This feature is only available in Ultimate.

To put it simply, with the capability at hand, the potential savings, IMHO, are 3 or more months per year per developer with Visual Studio Ultimate versus Visual Studio Professional. Especially if this is coupled with TFS, the time and cost savings are much more so across the organization from an Application Lifecycle Management (ALM) perspective. And just as importantly makes the developers lives more interesting, by taking out mundane aspects of development. This is not a proven statistic, just an estimate I'm collecting from my personal experience as a developer. This takes into account, that bugs are time consuming and costly to fix.

In a blog I posted several days ago (about Copy/Paste Issues) , there was some questions about Code Clone Analysis, an exciting  new feature in VS2012, however, yes it's only available in Premium and Ultimate.

For more information, please visit the following site, for detailed side by side comparisons. End hit "Expand All".

http://www.microsoft.com/visualstudio/eng/products/compare#feature-chart-heading