Although UPS and USPS offer overnight delivery, USPS Priority Mail Service has an average delivery time of just 1.7 days, whereas UPS Ground has an average of 2.75 days. Therefore, USPS is the better choice if your package is time-sensitive.
USPS Priority Mail®\n\n That said, it's also important to note that your Priority Mail shipment will be delivered more quickly than your UPS Ground® and FedEx Ground® shipments. USPS Priority Mail® is again estimated to be a two-day delivery while the others measure in at 4 days.