Bellissimo post di Ted Pattions sulla differenza tra SitePages e Application Pages.

In particolare Ted analizza le scelte di quando creare una sitepages piuttosto che una application pages e in breve sono:

The reasons to create pages as site pages

• The page must support customization through Web Parts
• The page must support customization through the SharePoint Designer
• The page must be added dynamically through code or through feature activation
• You must add multiple instances of the page to a site

The reasons to create pages as application pages

• You want to prohibit user customization
• You want to avoid safe mode processing
• You want to achieve the best possible performance

Inoltre vi consiglio di leggere l'intero post che è molto interessante