Adding users to both WordPress and Blogger is easy and offers bloggers the benefit of sharing posting duties. The process is also very different. Here are the instructions and the individual features of both.

Adding multiple authors to WordPress blogs

Adding multiple users to WordPress is easier to find and set up and offers more user roles than Blogger.

In WordPress near the bottom of the Dashboard is a menu link titled Users. From here you can view users, add new users and view your own profile.

Select Add New and enter the following information:

Username (required) - A username cannot be changed, however WordPress allows for nicknames which can be added and used instead of the assigned username.
E-mail (required)
First Name
Last Name
Website
Password (twice, required)

Tick the Send Password checkbox if you wish the new user to receive their password by mail.

Finally select a WordPress User Role.

Super Admin - Person with VIP access to a WordPress multi-blog network (think multi-authors and multi-blogs…large scale).
Administrator - Traditional WordPress admin with full administration features.
Editor - Generally, an admin’s assistant who can publish and manage posts and pages and manage other users' posts, etc.
Author - User who publishes and manages their own posts.
Contributor - Somebody who can write and manage their posts but not publish them. An Admin or Editor has to review and publish Contributor posts.
Subscriber - Traditionally a user who can read posts and can comment if restrictions require only registered users can respond (additional settings in Dashboard assist in setting up for anybody to register as a user and to limit comments to subscribers only)

Visit WordPress.org for additional detail on Roles and Capabilities. There is a great Capability vs. Role Table featured there.

Additional WordPress plugins can assist in further defining the various user roles.

If the user is unfamiliar with WordPress you can send a personal email with instructions and links on where to change their password and where to add their profile information.


Adding multiple authors to Blogger blogs

Select the Settings menu tab and then Permissions from the Settings menu bar.

Under Blog Authors which lists the current author as admin, click the Add Authors button and add the emails of the desired authors to invite to write on your blog. They will be listed as Open invitations under the current blog author/admin. There are options to invite them again if they don't respond and a link to remove them.

They will receive an email invite with a confirmation link to contribute. The email explains they must have a Google Account to confirm and start posting.

They will be added as an author to the Blog Authors listing once they follow the link. Another link allows the current admin to "grant admin privileges" to the author. Clicking this link returns the following dialog box with the option to grant admin privileges or cancel:

"Giving this person admin rights will allow them to edit this blog’s settings and template, as well as other members’ posts."

Granting the new author admin rights adds the "grant admin privileges" link next to the blog’s current admin (original blog author) as well. Admin privileges in Blogger are also a way to turn over a blog to another author altogether. If you are not careful and grant admin access to an author you do not fully trust your blog could inadvertently be turned over.

Comparatively both blogging platforms allow for multi-authors, however if blog management requires varying levels of leadership or duties, WordPress is more flexible.