USPS is the way to go. Just look at the condition of the boxes you receive and compare the services.
I have never had a problem with with Priority mail. Fedex broke a stock and paid for it and UPS mangles the boxes.
Even though Priority includes $50 insurance automatically, I always add some just to get the insurance sticker on the box.
Registered is slow and a pain to pack since you must use paper tape however you don't have to pay extra for insurance since it is automatically insured for $50,000 or that is what my Post Office said. Priority max insurance is $5,000.
