If at all possible, I always tend to go with USPS for shipping packages. Out of the USPS, UPS, and FedEx, I've had the best luck with the USPS over the years. Plus, if you're shipping books or dvds, you just can't beat the price for media mail. If I must, I'll go with FedEX over UPS after a certain incident in 2003.
My younger sibling had interned in NYC that summer and had taken the small microwave I'd had in my dorm room in college. As the sibling's internship was finishing up at the end of summer, I was moving out of the apartment I lived in my first year of grad school and into a new place. Neither the new roommate nor I had a microwave, so instead of shipping the original microwave back to our parents, my sibling just sent it on to me.
The microwave traveled all the way across country and made it to my town. Rather than deliver it (they claimed they tried, but they never left even one of those notes on the door that they'd been there and would try on another day) they put it back on a truck and sent it to the return address (my parents address). We had been watching the tracking and knew what was going on. We called and told them that the package had made it to my town, had been turned around before being delivered, and could they please send it back my way. It made it nearly my parents before they turned the package back around again and sent it 2000 miles back to me. This time it was delivered. The package was horribly, horribly mangled. I pulled the microwave out of the box and it was dented. I plugged it up and put something in it. It started emitting sparks.
Ok. Fine. The package had been insured, so I called UPS about filing a claim. I explained the situation. They told me that my sibling would have to physically go back to the UPS store in NYC that the mircowave had been shipped from to file a claim. By this point (the shipping the microwave back and forth across the country had taken several weeks), my sibling was already back in school in LA. We explained that my sibling had done an internship in NYC, was 3000 miles away from the said store, and that going in person was out of the question. We asked if there was something else we could do. We were told that we were out of luck and nothing could be done... The whole sitution was just ridiculous, as was the unwillingness of anyone we spoke to about the matter to be able to figure out a way to file our insurance claim. Seriously, was it really necessary for someone to physically go back to the store, especially since my sibling and I were 3000 miles away and our parents 1000 miles away?
Since that point, UPS has been my last choice in shipping.