It's not the service, it's the people. I've seen both UPS and FedEx deliver packages in pristine shape, or mauled to death. Over the holiday season, FedEx lost a shipment of tires, and on-line tracking said the package had no tracking information. We never got the delivery, but they told the tire company that it definately was delivered. I played phone tag all week to get a replacement order shipped.
US Postal Service is my choice, but only if I get Priority. :-)