One difference is that she cannot vote in elections, which may be a big deal or not depending on your personal philosophy on the subject.
Another difference is that a permanent resident cannot work for the US Government. So if your desire is to have your wife working at the Post Office, she will need to become a naturalized citizen first.
By the way, your wife will be eligible to become a US citizen as a spouse of a US citizen in as little as three years from the time she became a Permanent Resident.
One main reason for her to become a US citizen is if she wants to petition to bring other members of her immediate family, such as her mother or father, or brothers or sisters, to America under a permanent visa. She must be a US citizen in order to do so.
She can petition to bring her immediate family here under a tourist or visitor's visa under her permanent residency, but she cannot petition for permanent residency for them until she is a citizen.
Another difference between a permanent resident and a citizen is how you are handled in the event you are convicted of a crime.
A felony is defined as a crime where the punishment for the crime, if convicted, is a year or more in prison.
A citizen who is convicted of a felony may serve a sentence and may lose certain citizenship rights such as voting and the right to carry a firearm, but they do not lose their citizenship.
A permanent resident that is convicted of a felony has the same sentencing requirements as a citizen, but after serving their sentence, they may lose their right to be in the United States, and may be deported.
I know of a man who has a Russian spouse whose wife likes to shoplift. If you followed the recent Wynona Ryder shoplifting case, you are aware of the fact that she was convicted of a number of felonies.
If she had been a permanent resident rather than a citizen, Wynona may have been subject to deportation.
If this man's Russian wife were to take more than $500.00 worth of goods from a store, she could be prosecuted for grand theft, which is a felony. If she gets caught, she may be on a plane back home before she knows it.
I am not excusing her behavior, but I'm only warning you of the consequences of certain behavior. Shoplifting, or possession of controlled substances, or any other crime that may seem innocuous to someone, may still be a felony, and may result in your wife's deportation.
