User Control vs Custom Control in .NET

User Control:

• User Controls (.ascx) derived from System.Web.UI.UserControl
• Designed for single-application
• Deployed as .ASCX and source code of the application
• If the same control needs to be used in more than one application, it introduces redundancy and maintenance problems
• We have to use within the application and it rests in the application directory.

Eg:A much better choice when you need static content within a fixed layout, for example, when you make headers and footers

Custom Control:

• Custom controls derived from System.Web.UI.WebControls.WebControl or System.Web.UI.Controls
• Designed so that it can be used by more than one application
• Deployed either in the application’s Bin directory or in the global assembly cache
• Distributed easily and without problems associated with redundancy and maintenance
• we can keep it in the Toolbox and use it whenever we want

 More suited for when an application requires dynamic content to be displayed; can be reused across an application, for example, for a data bound table control with dynamic rows