Permanent residence generally permits green card holders to live and work in the U.S. without limitation. Many permanent residents therefore do not consider the benefits of citizenship, which include the right to vote, more favorable tax treatment (especially with respect to estate taxes), the right to hold almost any elected position, the ability to occupy any government job, and the right to obtain all forms of public aid and assistance.
In addition, the ability to assist family members who seek to immigrate to the U.S. is greatly enhanced by citizenship over permanent residence. Citizenship status increases the range of relatives that may be assisted, and, in many cases, the amount of time that is necessary for family petitions to be approved. Children of two U.S. citizen parents will automatically obtain citizenship status irrespective of where they are born, but this is not always the case for children born abroad to one U.S. citizen parent.
Citizenship status also guards against the possibility that permanent residence may be lost as a result of long periods of residency abroad, or the commission of a criminal offense. The standard for a conviction of a non-U.S. citizen may be broader than for a U.S. citizen, and permanent residents may be deported for having committed certain minor offenses.