I deal with both almost every day, running a small manufacturing business from our rural residential / farm-zoned property. On the phone or web, Fed Ex is easier and more helpful, but employs drivers who are just absolutely terrible.
I've dealt with probably 20+ different UPS drivers in my working life, having always worked in manufacturing with lots of goods going in/out, and they've all been very professional and very good at their jobs. On the flip side, the Fed Ex drivers I have to deal with are almost consistently sloppy, disgruntled, and downright reckless drivers.
If I had a way to prevent vendors from using Fed Ex, I would, just to keep their drivers off our property and out of our neighborhood. Unfortunately, some vendors default to them, and so they're not entirely avoidable.