Posted By:
Damianim a carrier...NOT a clerk,
but registered mail is the safest by far, the reason for time differences as i understand are where they go and how many are coming with it... those letters & packages sent this way are cataloged, sealed, & locked with metal serial numbered clips. The Truck drivers have to sign for them from the offices and they have to have them signed for by the receiving office or plant.. so all this signing and locking etc make for longer delays. Where as with normal stuff from USPS or UPS just go in a bin and off they go!
So possibly if only a few items are going from one plant to another there is less logging and transferring, and less delay.
But "It's in the mail."