Fed Ex usually delivers on time around here, we just never know to which house they delivered our packages. I'd not be exaggerating if I claimed their delivery accuracy was as bad as 50% in our neighborhood, which is strange, since there are only a half dozen houses on our road, with every address clear as day atop a mailbox at the end of each driveway. You'd almost have to try to screw it up.
In a few cases, I've received packages for people half way across town, like literally a mile or three away. I will deliver their packages to them when this happens, since I don't want to hose the recipient. But I only do it at my convenience, like the next time I'm headed out that direction. So they probably report them missing before I get them delivered, as often as not.
We used to see Fed Ex sometimes showing packages as delivered, when they had not been. Then the package would show up the next day. All we could figure was a driver wanted to quit early but not get in trouble for late deliveries, so they reported them as delivered, and then finished the job the next morning.
We never have any of these problems with UPS, only Fed Ex, but these issues are probably all local... unique to our driver(s). Someone elsewhere in the country may experience the exact opposite, comparing these two companies.