My order of preference for shippers:
1. UPS. Great, up-to-date online tracking, and I know my delivery guy and my stop is one of his last, so he comes when I'm generally home (after 6:30PM). Even if they come early, they know how to get into the apartment building, and leave stuff at my front door (of my apartment, which is secure-entry, as opposed to in front of the building, which is not).
2a. USPS. Bad online tracking, especially in Los Angeles. Updates are posted hours after they're met (i.e. Out for Delivery at 10am often posts online at 3-4PM). Sometimes they're inaccurate as well. Couple of times it has said "out for delivery" and "undeliverable" and when I went to the post office the next day, they said "oh the system does that, it is probably on the truck to be delivered today" and it was. Their big upside is that they put packages in my secure mailbox.
2b. Fedex. Great online tracking, but always comes during the work day and usually requires a signature, necessitating me to have it held for pickup. On packages not requiring a signature, they'd be my solid #2 as they get into the building and deliver to my front door.
3. ONTRAC. Seems to only partner with Amazon for select western states. Fast delivery, decent online presence, had an initial problem getting into the building but that seems to be fixed. Tends to leave stuff in shared mailbox area out in the open which I don't like: yes it's behind the secure entry but there are 45 units in my building and some may be a theft risk.
4. "Amazon enterprise service" or something like that. I'm curious if this is their Amazon Fresh trucks, as the tracking number tends to be TBA#######. Also, never saw this until the Fresh service started around Los Angeles and I saw their trucks driving around the area, so that's why I think it may be them. They rarely ever bother to get into my building and just leave packages on top of the call box outside. One time I saw my package and got it. The other time it went missing and Amazon had to send me an overnight replacement.