None of them have been perfect for our shop's needs. USPS has consistently been the worst, UPS the best. FedEx somewhere in the middle, but closer in result to UPS than the post office's tawdry performance. Most issues have been with inbound deliveries, both with ordered goods and with inbound FFL transfers initiated by others elsewhere. Twice delivering guns to the Salvation Army instead of us...that's the post office for you. Maybe it's the 'Army' in their name that confused the carrier. But both FedEx and UPS have screwed up gun deliveries as well.

As for outbound packages we use UPS far more than FedEx but that's primarily because UPS gives us a far better rate package than FedEx does. It almost always comes down to costs with the shop owner.