Sql Server Performance Degradation in moving from 2005 to 2008

I have sql server 2005 setup for my performance bench marking exercise and I have put same database on another server which has sql server 2008 and exact replica in terms of hardware configuration. Sql server memory allocation is also same in both servers. But my benchmarking results are worse on 2008 than 2005. Will somebody help me to find the reasons for performance degradation in sql server 2008. What are the thing I need to take care, or parameters to set for getting the better or same result sets.

Did you rebuild indexes and statistics after setting up the database on SQL Server 2008?

It's mentioned on MSDN (see "Next steps")

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Next Steps

After you upgrade to SQL Server ...

Update statistics — To help optimize query performance, we recommend that you update statistics on all databases following upgrade. Use the sp_updatestats stored procedure to update statistics in user-defined tables in SQL Server databases.

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StackExchange Database Administrators Q#9910, answer score: 5