They both have the exact same published retail rates for Ground packages. Surcharges are the same as well I believe. For residential delivery, Fedex does Tue - Sat, while UPS does Mon - Fri. Fedex will get to most places in the 48 contiguous states within 3 days. The 3 day delivery area for UPS is less than Fedex.
I love my UPS guy. I hate the fedex guy because he sometimes lies about delivery attempts. On several occasion they have claimed that no one was home when I in fact I was waiting near the door the entire day.
fact: UPS drivers are not allowed to do a left turn as it's more efficient in some ways to plan their route by avoiding left turns.