1. A registration on the Principal Register is constructive notice of a claim of ownership which eliminates the defense of good faith adoption by a third party. On the other hand, a registration on the Supplemental Register has no such evidentiary effect.
2. A registration on the Principal Register is prima facie evidence of the Registrant's exclusive right to use the mark. On the other hand, a registration on the Supplemental Register has no such evidentiary effect.
3. A registration on the Principal Register may become incontestable after five (5) years of continuous use after the date of registration. On the other hand, a registration on the Supplemental Register can not achieve such evidentiary status. However, after five years of substantially exclusive use of a mark, a registration can be obtained on the Principal Register subject to § 2(f) of the statute (prima facie distinctiveness through use).
4. Only a Principal Register registration may be used as a basis for the Department of the Treasury to stop importation of infringing goods into the United States.
5. Currently, only a Principal Register registration may be asserted pursuant to the current internic dispute resolution process. This however is in a state of flux at the moment and may change. Should this ever become an issue, Principal Register registrations can be obtained in many foreign countries that have only minimal substantive examination.

Supplemental Registration Advantages

1. An infringement suit can be brought in Federal Court.
2. A claim for unfair use and competition can also be brought in Federal Court.
3. Issues of validity and ownership in an infringement action are governed by Federal statute.
4. The Trademark Office can refuse registration to a subsequent applicant of a confusingly similar mark on the basis of a Supplemental Registration.
5. Trademark searches will list a Supplemental Registration.
6. A registrant is entitled to use ® to put the world on notice of its registration.
7. A Supplemental Registration can be used as a basis for registrability (prima facie presumption of acquired distinctiveness) on the Principal Register after five years of registration.