Usually I prefer UPS simply because my local post office is insanely incompetent. Things are even easier for them because I have a PO Box, not a street-mailbox delivery.
However, even when I bring print outs of the tracking from usps.com saying available/ready for pickup, etc...they still cannot find it. I've had more than 6 packages "lost" temporarily between August and today, only to be "found" after 45 minutes of battle with the incompetent Postmaster. It's always the same script...first it went out for delivery then I tell them I haven't had street delivery in over 20 years at my address...then it's not sorted yet then it's out for delivery again, etc...when they realize I am not leaving, then they get off their arse and go look. 45 minutes later it's a miracle! There it is. Right where I said it'd be.
Priority Mail is a great service, just not in my area. Also, my UPS driver has been with us for more than ten years and always rings the bell and leaves it in sensible places should someone not be here to accept it.