UPS drivers are teamsters and are pretty committed to the company. You need to work your ass off in distribution centers and other places before you get in a truck.

When FedEx was falling behind by not having ground service, they bought another network (RPS iirc) and built out a network of contracted providers. In my area, it was the companies that did newspaper delivery. Some of them are ok, most of them suck. I think the residential delivery is all contracted, but business services are FedEx badged people in some scenarios.

UPS drivers are unionized. FedEx drivers at the local stage are a network of third party companies that contract to FedEx and put their logo on their trucks. Look at the grey fine print by the driver door.