I'm an electrical engineer and I design buildings for a living. I prefer the NEMA 5-20. Chances are, the plug in your office is a NEMA 5-20. The difference is in the ampacity rating, 15 amps and 20 amps. You can tell which is which by the plug configuration. Does your plug have a small horizontal slit on the right vertical slit? If so, it's a NEMA 5-20. Several commercial cleaning and kitchen appliances require 12 amps are more so the NEMA 5-20 is preferred in those applications. Don't worry if your house only has NEMA 5-15 plugs with a 20 amp circuit breaker protecting it. Residential appliances are rated to be used with a NEMA 5-15 plug.