Based on your provided reference, I would agree. However, if one examines execution plans for these two queries and run them together, the query optimizer treats them as the same execution plan and equates both queries to the same cost.
Here is a nice resource on the topic:
http://sqlinthewild.co.za/index.php/2009/08/17/exists-vs-in/
Jason...AKA CirqueDeSQLeil
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I have given a name to my pain...MCM SQL Server, MVP
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