rupeshhari is right. Inside Canada a PR has the same rights as a Canadian citizen except to vote but when you are outside Canada, PR does not equal citizenship.
Here is the link to the visa information to the US for Canadian citizens and PR's:
http://travel.state.gov/visa/temp/without/without_1260.html
Permanent residents (aka landed immigrants) of Canada must have a nonimmigrant visa unless the permanent resident is a national of a country that participates in the Visa Waiver Program (VWP), meets the VWP requirements, and is seeking to enter the U.S. for 90 days or less under that program.
So basically, reading that, there is really no benefit being a Canada PR in order to visit the US.
Canada however does not require US PR's to have a visa to visit Canada. You can find that information at http://www.cic.gc.ca/EnGLish/visit/visas.asp where it says:
Many people do not require a visa to visit Canada. These include:
* persons lawfully admitted to the United States for permanent residence who are in possession of their alien registration card (Green card) or can provide other evidence of permanent residence;