I was the global logistics manager for a $500-million chemical company, and we used FedEx and UPS to the tune of $10,000-$15,000 per week - and that's with a huge discount. First Rays uses FedEx almost exclusively domestically, averaging between $350-$500 per week with a moderate discount.
The chemical company had on average, one damaged package per month with UPS, about one a year with FedEx (I fired UPS). First Rays has had one package lost and two damaged in over 10 years. There was another occasion where a package - plants, of course - was dropped in the snow at the end of a private road, rather than at the house, 2 miles up the road.
Before going with FedEx, I shipped for about 7 years with the USPS, and I experienced more losses and delays (an important factor when shipping plants) than I ever have since. With their financial woes, I cannot see it getting any better.
FedEx Ground and Home Delivery drivers, and all UPS drivers are not employees, they are contractors who bid on the routes, and own, fuel, and maintain the trucks they drive. Bitch about service issues, and they will lose their routes. The guy in Utah who dumped the package rather than a complete delivery lost his.
When I ship to Canada, I usually use the USPS, precisely for the cost factor. As a non-resident importer, if I go through FedEx, I have to collect taxes and duties, and have a brokerage fee to deal with as well. Even with that, sometimes it's cheaper than the USPS, so I use FedEx in that case - I always run the costs both ways to find out.
Delivery times to Canada differ greatly, too. I recently sent two packages to the Toronto area on the same day - one FedEx International Ground, the other with the USPS. The FedEx package got to the gateway in two days, cleared customs the next day, and was delivered two days after that. The USPS package took two full weeks to arrive. I can also track the FedEx package en route. Can't do that with the USPS.