What are list forms and form library forms?

SharePoint list forms store data directly in a SharePoint list.  Each control (e.g. text box) in the form is bound to a column in the list. SharePoint list forms are directly connected to the list, which means that you don’t have to worry about setting up the publish and submit locations.
Form library forms store data in XML files in a SharePoint form library. This means they are more flexible and you can do more with them. For example, they can be configured to save drafts and submit to different locations. However, they are more complex to work with and require more decisions to be made during configuration.
Because the way data is stored between these template types is different, it is not possible to switch between them.

Guidelines

Here are some basic guidelines to help you decide what type of form to design.

Use a list if:

• You want to quickly get started building InfoPath forms on SharePoint
• You need to use your form offline with SharePoint Workspace (formerly Groove)
• You want to filter your SharePoint list based on a person or group
• You would like to use the built-in display / edit views

Use a form library if:

• You have repeating or nested data
• You are working from a predefined industry or complex schema
• Your form needs to be digitally signed
• You need code in your form
• Your form is not hosted in SharePoint or you need to store results as an XML document