MSSQL Tiger Team – Plan Comparison Tool
I ran across the above link detailing the execution plan comparison tool included as part of SSMS(SQL Server Management Studio). This tool gives you a way to view two execution plans at the same time, along with displaying statistics from each plan.
Once you produce the first execution plan, you can right-click and select ‘Save Execution Plan As…’ and save the plan as a .sqlplan file. Once the second execution plan is generated, you can right click on the plan and select the ‘Compare Showplan’ option. The dialog opened will allow you to select the file with the first plan, and will open the comparison tool to display the two plans.

On the topic of execution plans, SQL Sentry announced recently that their Plan Explorer tool is now free, If you haven’t used this tool, it is a great improvement on viewing SQL Server execution plans.
SQL Sentry Plan Explorer