I heavily favor the USPS for anything standard. If it's something that I require tracking on, then I will use FedEx or UPS.
FedEx and UPS in our neighborhood both suck donkey nuts. The drivers are ornery. Half the time, they launch the package from the driveway onto our porch 10-15'. The UPS driver once got angry at my wife because she couldn't help him get the heavy box out of his truck, while she was seven months pregnant.
The USPS driver, on the other hand, is always happy and chatty. Always says hello and have a nice day. A neighbor who has had health problems says she asks him how he's doing.
And as for deliveries, almost never have problems with USPS. FedEx lost my entire toolbag (well, someone stole it, I'm sure). FedEx and UPS have both missed deliveries. And UPS had a long streak where tracking would say a package was delivered, but it didn't show up on my porch for another 6 hours.