I ship everything from my online store USPS Priority Mail, unless I absolutely have to use UPS. I've found Priority Mail to be more reliable than UPS, faster, and less expensive. This runs counter to conventional wisdom about government-run entities, and most people don't believe it, either.
Here's an example, though. On Saturday 12/22, I ordered at new stylus for my turntable. It was shipped UPS. But UPS was closed on Monday and Tuesday for Christmas, so it didn't ship from Nevada until Wednesday the 26th. The estimated shipping time is 4 days, which puts delivery at Thursday, January 3rd, since UPS is closed Monday and Tuesday for New Year's. So, the time from placing my order until delivery will be 12 days.
I placed an order for speaker parts from one online store on Christmas day (Tuesday), and another order at another place on Wednesday the 26th. One place was in Florida, the other in Oregon. Both shipped Priority Mail, and both arrived yesterday (Friday). Time from order until delivery was 3 and 2 days respectively.
The postal service was working Christmas Eve day and will be working New Year's Eve day. Thanks to the union, UPS will not.
It's no wonder UPS is trying to force FedEx to unionize.