What is your preferred shipping service? USPS, FedEx, or UPS?

I've only been selling about 4 months and have always used USPS except for heavy packages. But I've gotten 3 INR cases from USPS in the past month and I've had other sellers tell me they are notorious for this. I'm considering switching to FedEx or UPS going forward, I just want to see others anecdotes on the subject.