The Key Manager is basically designed to always be able to do everything, without any loss of functionality. Where as Admin’s can be changed to be whatever you would like them to be.
If you want the side by side comparison:
$roles->add_role( 'keymaster', __('Key Master'), array(
'use_keys' => true, // Verb forms of roles - keymaster
'administrate' => true, // administrator
'moderate' => true, // moderator
'participate' => true, // member
'keep_gate' => true, // Make new Key Masters //+
'import_export' => true, // Import and export data //+
'recount' => true, // bb-do-counts.php //+
'manage_options' => true, // backend //+
'manage_themes' => true, // Themes //+
'manage_plugins' => true, // Plugins //+
'manage_options' => true, // Options //+
'edit_users' => true,
'manage_tags' => true, // Rename, Merge, Destroy
'edit_others_favorites' => true,
'manage_forums' => true, // Add/Rename forum
'delete_forums' => true, // Delete forum
'delete_topics' => true,
'close_topics' => true,
'stick_topics' => true,
'move_topics' => true,
'view_by_ip' => true, // view-ip.php
'edit_closed' => true, // Edit closed topics
'edit_deleted' => true, // Edit deleted topics/posts
'browse_deleted' => true, // Use 'deleted' view
'edit_others_tags' => true,
'edit_others_topics' => true,
'delete_posts' => true,
'throttle' => true, // Post back to back arbitrarily quickly
'ignore_edit_lock' => true,
'edit_others_posts' => true,
'edit_favorites' => true,
'edit_tags' => true,
'edit_topics' => true, // Edit title, resolution status
'edit_posts' => true,
'edit_profile' => true,
'write_topics' => true,
'write_posts' => true,
'change_password' => true,
'read' => true
) );
$roles->add_role( 'administrator', __('Administrator'), array(
'administrate' => true,
'moderate' => true,
'participate' => true,
'edit_users' => true, //+
'edit_others_favorites' => true, //+
'manage_forums' => true, //+
'delete_forums' => true, //+
'manage_tags' => true,
'delete_topics' => true,
'close_topics' => true,
'stick_topics' => true,
'move_topics' => true,
'view_by_ip' => true,
'edit_closed' => true,
'edit_deleted' => true,
'browse_deleted' => true,
'edit_others_tags' => true,
'edit_others_topics' => true,
'delete_posts' => true,
'throttle' => true,
'ignore_edit_lock' => true,
'edit_others_posts' => true,
'edit_favorites' => true,
'edit_tags' => true,
'edit_topics' => true,
'edit_posts' => true,
'edit_profile' => true,
'write_topics' => true,
'write_posts' => true,
'change_password' => true,
'read' => true
) );
