The CDC says condoms are 12% to fertility awareness's 24% (i.e. twice the risk). http://www.cdc.gov/reproductivehealth/contraception/unintend...
That means fertility awareness has worse odds than Russian roulette.
I'm not the slightest bit interested in perfect use failure rates, because humans are rarely perfect (especially not the ones who think they are), and the consequences of a whoops are pretty immense, both for the couple and for the unwanted child that results.
Meanwhile, an implant has a 0.05% typical use failure rate, and an IUD 0.2%. I'm not taking any chances - I'm infertile, have had a vasectomy, and my wife has an IUD. My current set of twins (via donor sperm) are plenty of work for my liking.