UPS is great most of the time, just be aware that during the Christmas holidays it may be different. Loaders are super rushed filling the trailers at night and if a small package slips closer to the bottom, a larger and/or heavier package may end up on top. Not a pretty sight at all when the trailer is unloaded.
All of them have issues occasionally, USPS sent a package in a detour to Boise last year, before going up 101 for a "short" ~180 mile trip and arriving a week later. A bicyclists would have been faster. Regarding damage, UPS decided to see how flexible a package was a few months ago... good thing it was a grape vine, but the bamboo support stick broke! Ever try breaking a 1/4 inch bamboo?

Concur that good packing helps a ton.
For anything larger than seeds or seedlings, I tend to go with UPS for this reason. They're generally cheaper for larger packages, and usually always handle them better.
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