DISQUS offers certain advantages like being able to create one account (as a commenter) and post on thousands of blogs/sites without registering, while keeping a comments history for your profile. Other advantages are video comments via the integration with Seismic and some goodies like comment rating and the list goes on.

If you want a solid comment system for your site that is based on an online service and don't bother NOT having a members area linked to the commenters, DISQUS is great. If you want more control and better integration, Azrul's JomComment is the only way and we highly recommend it. ;)

It depends on your needs/priorities.  :D