Is the role set using wp_update_user or set_role for membership & pro sites plugins?

Hi
Question-
How is the role set for Pro Sites and Membership plugins?

Background-
I want to change/ add some new fields to a member's profile. I found this plugin User Meta but noticed in their forums that changes will be lost if the role is set using wp_update_user (http://wordpress.org/support/topic/does-wp_update_user-delete-user_meta)... in a nutshell...

"You must set their role using set_role in the WP_User class. If you change their role via wp_update_user, you will lose any "CUSTOM" user_meta information you may have collected in a CUSTOM registration form."