Creating Secure Extranets Using Drupal Organic Groups, LifeRay Social or Alfresco Share

Question

We are using Drupal to build a portal site and want to offer secure extranets to users so that users from different companies can collaborate on projects.

We would like to offer the following functionality for the extranets:

1. Ability to make extranets public or private and to invite new members easily.
2. Typical extranet features such as calendar, contact list, task list.
3. Shareable and encrypted document folders, which can be metered to identify amount of storage (document folders need to be highly secure).
4. Ability to add to functionality of extranets either using a "features library" (such as offered through www.openatrium.com for Drupal) or portlets (such as for LifeRay Social).

Questions: Which tool --Drupal Organic Groups, LifeRay Social, Alfresco Share, other -- would you recommend and why?