express vs priority mail usps refers to two different USPS shipping services with distinct delivery speeds and costs. USPS Express Mail is an expedited service that guarantees next-day or two-day delivery, depending on the destination. It includes tracking, insurance, and delivery confirmation. USPS Priority Mail, on the other hand, offers a more affordable shipping option with delivery in 1-3 business days. Both services provide reliable options for sending packages quickly, but Express Mail is the faster and more expensive choice.