One of the questions that often comes up in SharePoint engagements is the question of whether you should create your own site definition or whether you should use the out-of-the-box definitions and use features to control how they appear. It is in fact a topic of some discussion between SharePoint consultants. My hope here is to illuminate the primary reasons that you should be creating site definitions -- and what reasons you shouldn't create them. Let's start our discussions about using features to modify a site definition.

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http://www.intranetjournal.com/articles/200808/ij_08_04_08a.html