From my expirience ( 10 years with AAC, BRB and 17 years with ABC) can tell you-AAC is easier to make more torq ( for torq type aplication), BRB much easier to get top speed and last much lomger ( no need to buy new set, just keep replacing pistons) and ABC is just avarage power and life. AAC is more dificult to handle-small mistake and sleeve is bent.
In RC cars I found AAC much better works on tight tracks and BRB s more for high speed tracks. But in the mean time BRB can easy bring 8 minuts run time. There is a lot of thing behind material set ups and everything has logical explanation.
Defenetly price for BRB and AAC is higher in AAC case due to more dificult process to plate it by chrome and BRB is due to price of Berilium bronze. Bu t final price got to be no more then $10 difference between BRB, AAC and ABC.
I perconaly run only BRB and AAC sets and feel much more comfortable then with ABC-I can set engine for any track ( custom set ups ) within 10 minuts and will know -this is the best possible from particular engine.