Amazon recruited a huge number of Walmart executives, to the point that Walmart sued Amazon. I expect it has also poached a large number of FedEx and UPS execs. The problem for UPS vs Amazon is that UPS is unionized, whereas Amazon is not. Amazon has the potential to become a big shipper for non-Amazon website shipments alongside FedEx and UPS. Whether it moves in that direction depends on how confident it is that becoming that huge in the shipping business is compatible with avoiding unionization. Its package handling side is already getting a lot of political static regarding work conditions. Its workers are probably getting paid about as well as union workers, but they are the best of the best in their category, the product of a gruelling weed-out process that has eliminated most of the less productive workers that tend to find a secure niche in union work forces like UPS’s, thereby dragging down UPS’s gross margins, with potentially company-ending consequences in a price war.
I find in my local that UPS is SLOW compared to FedEx and USPS. So slow that I call them the Slowest Ship in the Shipping Business. I just ordered something on Oct 10 that weighed 20lbs that wasn't even eligible for "Prime" shipping and I got it Oct.12th. California to Illinois - delivered by USPS. UPS doesn't deliver on weekends around here either. They better shape up.
Businesses rely on UPS for several services. The USPS and Amazon use UPS for some deliveries. Although Amazon wants the residential market, they cannot provide to businesses what UPS does.
So I look for UPS to be around awhile.