So then let's summarize the way things seem to be working in the semi-retail package biz now:

There are really only 3 games: USPS, FedEx, and UPS. Everybody else of consequence has gone away or been assimilated.

USPS ships stuff via FedEx as the contract hauler. Presumably some of that goes by air to MEM and back, but read on. USPS has a few other things that are different: they deliver everywhere (noplace is too far out in the boonies); 1st class mail, which the others are forbidden to carry by law (so what's a Priority Mail package - isn't that the package equivalent of 1st class?); to get any kind of tracking you have to pay extra, or use one of the parcel services that provide it - usually nearly the same cost as UPS, but notably less than FedEx; USPS delivers on Saturdays for no extra charge and for extra $$ you can even get Sunday/holiday delivery. However, their target (not guarantee) for 1st class mail (and Priority?) now is 2-day delivery, even within the same sorting center's area, and 3-5 day delivery over longer distances. If you want overnight, use Express Mail at about the same price as UPS' and FedEx's air offerings.

FedEx does more by air than the others, and even might now be carrying the USPS' "air mail". But they also have FedEx Ground which is almost exclusively trucks. If FedEx is using intermodal trains, there would have been foaming about it in the fan and industry media - there isn't so they don't. Ground generally takes 2-3 days even within a few hundred miles. They apparently have a SurePost-like setup (similar to UPS') for delivering residential parcels via USPS rather than by themselves, though if FedEx actually delivers to the local post office rather than the regional sorting center they might save a day or so over UPS.

UPS uses air, intermodal train, and truck extensively, and SurePost (UPS hub-USPS sorting hub-localPO-destination) for residential Ground deliveries. They have several big hubs for air shipping instead of one huge one (I see regular flights into Mather from Louisville, Des Moines, Columbia, and the Ontario-Mather-Reno shuttle, and from other places during the Xmas rush); use trains extensively for cross-country runs (the Z-train system: has UP recently taken that over from BNSF?) because they can reliably get large blocks of stuff from Chicago to the west coast in 50-60 hours or less without having to pay for team drivers, but are apparently willing to do team drivers in big rigs if the timing requires it; and are willing to bypass the big hub system for short-medium distance stuff on the ground (breakpoints seem to be around 250 miles for short, up to 450 or so for medium) which reduces shipping time. UPS Ground costs more than Priority Mail (though not by much), costs less than FedEx even Ground, and is faster than both if shipping to a business in the short- or medium-distance zones (typically next-day delivery short-distance, 2nd-day in medium-distance zones).

Since most of my package shipments have been fairly small and in the short-distance zone, I usually use UPS Ground - reasonable price, UPS store is nearby (shipping until 4-5 PM), service with a smile instead of a snarl, and for business addresses it gets there tomorrow without having to pay the air or Express Mail premium. I've considered USPS for several shipments but they don't seem to have benefits or low enough prices to justify driving to the P.O. across town (the local supermarket USPS desk doesn't accept packages over 5 lb. or so, and their closing time is about noon). FedEx (nee Kinkos, another drive across town) is just overpriced and underperforming for my particular needs. YMMV of course.

And of the group, the only one that uses trains (now that USPS does its line-haul via FedEx) is UPS. Foamer consideration. Does UP actually have the UPS business now? If so, then train from Rockford-Richmond in 50-55 hours is within the tracking window for my package.