I too have had time problems with USPS, it seems every third time I send something it takes twice or three times as long as it should. I would like to thank at least 4 forum members who DIDN'T start calling me a cheat and a rip-off artist when their packages were late arriving, and stuck with me and didn't flame.
As for UPS. I have a friend who worked night-shifts at UPS in the package conveyor/truck loading areas. I asked him about how they treated the packages and generally what the package did from step to step. Here is what I got out of him.
First off they treat packages like crap. The small boxes, that can be palmed, are tossed around like oversize softballs, that is why you see lots of smushed corners on your UPS stuff. These hooples are literally throwing these to the guy stackign boxes. You also get a RAISE if you can pass a zip-code test, that helps the packages get sorted faster in-line, this test familiarizes them with zip-codes obviously.
As for the truck, this is what goes down. The packages are stacked in rows as tall as the truck can accept, and lined up by the bay doors. They stack them ANY WAY they can, ensuring they are the correct height and depth of rows to fill the truck. Most of these USPS people are from poor neighborhoods. Often african american, spanish, caucasian races and really take no pride in their work. Their supervisors only care about time, and NEVER do the men handling boxes get in trouble for damaged goods. So what do they care, they never even hear about the broken stuff. UPS is crap. IMO you want good service and good insurance that won't hassle you, you gotta pay the bucks. Airborne Express and Fed-Ex are the best IMO, but they are ridiculously expensive. If I could afford it, I would use them for all items, but I am not a rich man so USPS still gets my money.
One tip (for USPS), get certified mail, or buy insurance, or send it registered mail. You got a leg up if you get one or more of these and it is only a touch extra, and still cheaper (AND SUPPOSEDLY FASTER) than UPS.
JC