I think that one of the major differences between the two companies is in each's corporate sense of humor. Whereas FedEx has always displayed an easy, fun-loving approach to their commercials, UPS has always just had straight-forward, no-nonsense approach.
One of the sayings you always hear at FedEx flight training is: "well, nobody has ever done that before", usually heard after someone gooned up some profile, landing, cross-wind takeoff, etc. It's a way of making lite of the error, so that the person making the error doesn't feel any worse than they already do.
Another perfect example of corporate culture can be seen in the following story: back in 1989 (or 90), when I was flying for UPS, someone forgot to tether the nose strut of a 747 to the ramp in SDF. Shortly thereafter, the loaders misloaded the jet, resulting in it sitting on its tail. Someone with a sense of humor took a photo of the jet, nose high, and made a bunch of photocopies, which magically started to appear around the training building and flight ops (and I assume other places within the sort as well.) Anyway, shortly after the photos started to appear, a letter was written and posted that said (in effect) "if we find out who took that picture and who is posting it around, that person will be fired." Each time the photo appeared, it was immediately taken down.
I left UPS in early 1990 and started at FedEx in late 1990, and sure enough, shortly thereafter, someone in MEM forgot to tether the nose gear of a DC-10, and you guessed it, they then misloaded the jet and it too landed on its tail. Again, someone took a photo and posted it all over the place, but this time with a small caption near the cockpit window (on the photo) saying: "DC-10 lands on its tail when the Captain throws his wallet out of the window." That photo stayed up in flight ops for a year or two, and everyone got a great laugh. Thankfully nobody was hurt in either incident, but I'd bet someone was fired at UPS and someone was told: "well, that's probably never happened before" at FedEx. Therein lies the difference with the two companies. That, and of course, you guys wear that horrid brown uniform.
JJ