Last night before RFF ate my post as a result of timing out while I was posting, I completed an anlysis of each Amazing Race according to the sunnyca point system. I normalized the results by dividing to get the average score for F/F teams and for other (M/F and M/M) teams. They showed pretty much what you already know per the snippets cited by sunnyca above. The only seasons where F/F teams ahead on that score were AR11, AR10, and AR5. AR4 was close but no cigar. Here is the points summary:

AR1 - Emily/Nancy 7, Pat and Brenda 3, Kim and Leslie 2 out of 11

AR2 - Peach/Mary 6, Peggy/claire 3, Deidre/Hilary 1 of 11

AR3 - Heather/Eve 4, Gina/Sylvia 1 of 12

AR4 - Tian/Jaree 7, Monica/Sheree 6 of 12

AR5 - Linda/Karen 8, Kami/Karli 7, Charla/Mirna 6 of 11

AR6 - Lena/Kristy 3, Meredith/Maria 2 of 11

AR7 - Debbie/bianca 3, Megan/Heidi 2 of 11

AR8 - Not Applicable

AR9 - Dani/Danielle 4, Wanda/Desiree 3, Joni/Lisa 2 of 11

AR10 - Dustin/Kandace 10, Lyn/Karlyn 9, Kelli/Jamie 2 of 11

AR11 - Dustin/Kandace 10, Charla/Mirna 9 of 11

AR12 - Shana/Jennifer 5, Marianna/Julia 3, Kate/Pat 2 of 11