Nexus, IIRC, covers only entry from Canada and costs $50 to apply. Global Entry covers entry from any country, costs $100 to apply.
Here's a link to the Homeland Security page with info on the various programs--all of which are valid for 5 years.
Global Entry requires an in-person interview, following "pre-clearance." It can take months for the pre-clearance to come through, and then another wait for an interview appointment, (days, weeks, or months depending on where you are aiming to do the interview). Unless you're flying home from another country anyway in which case you can do the interview without an appointment at many US international airports.