Great point!
USPS not only delivers xyz package quicker from the same to/from zip, but they are the only of the three that will actually deliver packages early than originally promised.
UPS and FedEx only, and I mean only, deliver on-time OR later than promised. NEVER earlier than promised. Additionally while UPS and FedEx say that there is a daily cut off time, this is almost always meaningless in that the first day never counts towards time-in-transit (which ,in terms of days, is already way longer than necessary from the start).
They both act as if they were to occasionally deliver a ground package a day earlier it would keep people from using their outrageously priced 2-day and next day services. Ie 13$ ground vs $137 next day.
Additionally UPS and FedEx (in my case mainly FedEx) are the only two where a package (generally on Saturdays) will get marked as “recipient not home” when I’ll check my cameras to see they never even attempted delivery.
both of their “guaranteed” time in transit maps are not worth the pixels upon which they are rendered.