You pay through the nose for all the extra services, such as on-line tracking across intl. borders, use of forwarders, delivery commitments, etc. The extra service is worth it for overseas shipments, but for low-priority items of low value to Canada/Mexico, don't bother. For shirts, USPS is fine. If you must have it delivered by a certain date, FedEx, Airborne, and DHL are better.
It's true UPS and USPS lose parcels, but they do have a lot of volumn. FedEx losses packages as well, but since their volumn is lower, you don't see it as much overall. But FedEx has one hell of a tracking system. UPS is still trying to catch up.
Watch out for multi-package COD shipments. To save money, some shippers only place COD on the first box. When the shipment reaches the consignee, he accepts everything but the COD box, and you're out the money.
The only reason I know this stuff is because I'm in the logistics software business.