The experts at Shipware (www.shipware.com) compared UPS and FedEx published rates for Air/Express services. For key weight range of 1-30 Lbs, UPS is cheaper as follows:

Average Net Differential for Key 1-30 Lbs Range (UPS v FedEx)                   UPS Lower By:
Next Day Air v Priority                                                                                        3.06%
NDA Saver v Standard Overnight                                                                         2.01%
2DA AM v 2 Day AM                                                                                          3.02%
2DA v 2 Day                                                                                                      3.14%
3DA v Express Saver                                                                                         13.99%