Mold Breakers advantages aren't that big as the biggest deal is propably Bronzong and hitting random levitators with EQ (like the rotom formes) wich isn't bad as Ono is mainly a choice band pokemon so you don't have to switch out against these pokemon.
So IMO Mold Breaker is often the more reliable Ability as opposed to Rivalry wich can give you a huge boost, but can also cut your damage down wich can cost you important KOs and at worst even the match.
I stand corrected on the Rivalry boost. However.
Why would you want to hit other levitators like Rotom-H when Outrage will likely OHKO them anyway?
Levitators worth noting include Gengar, Weezing, Flygon, Claydol, Latios, Latias, Mismagius, Bronzong, Rotom-H & company, Mesprit, Uxie, Azelf, Cresselia, and Sanzadora.
There isn't a single Pokemon there
other than Bronzong that resists Outrage but is weak to Earthquake. Most of these are OHKO'd by Outrage to begin with. Weezing might be able to survive a single hit, but that aside it isn't doing much, and it'll be 2HKO'd for sure.
Again, I'm not seeing the merit for Mold Breaker as far as Levitator is concerned.
Also, most people usually keep their Pokemon consistently male unless they're using female exclusive Pokemon. The most notables ones happen to be Latias and Blissey, who won't be able to handle hits from Outrage even with a .8 multiplier added.