This replaces your standard custom post meta form. Allows extension of page, post and custom post type by allowing you to create customised post form fields when adding or editing post types.
This is typically for developers to extend your typical post and post type form. You can use get_post_meta function in your theme template to display the saved data.

WP Extra Fields

Allows extension of page, post and custom post type by allowing you to create customised form fields to include when adding or editing post types.

jphase

WP Modification History enables a metabox that shows modficiation history by date/time, user, and the values that were modified. The modified values are shown in a diff format so that you can easily see what lines and characters were modified, deleted, added, etc.
Within the settings page, you are able to toggle off/on meta values in the event you don’t want certain things to be tracked when hitting the update button on that post type.
Possible future features:
<ul>
<li>Additional settings and display options (AJAX pagination, limit of results per page/metabox, etc.)</li>
<li>Comments and remarks on a particular revision</li>
<li>Email notifications when specific changesets are made</li>
<li>Stats</li>
</ul>

WP Modification History

WordPress Modification History adds a metabox that shows modification history on a particular set of post types.

WP Extra Fields vs WP Modification History