Which pill is better? belara or yasmin? or are all birth control pills 99.9% effective?

Choice of pills: Is done usually by the side effects rather than efficacy at preventing pregnancy. Birth control pills are theoretically effective up to 99.7% but in real world situations (due to forgetting to take, incorrect starts, etc) can be as low as 90%, and that shouldn't differ much amongst different pill formulations unless one is very large where higher-dose pills may be needed to control the cycles