None will give you 100% per _each_ mile (on L class), and 'better' is such a relative term in this matter, because not all miles are equal. It isn't just a matter of 'Arline XX gives me more miles than YY', it's what you are entitled to do with those miles what counts. It matters very little if, say, BA gives you 10 miles and AA only 7 if later BA will charge you 15 miles for the same award that AA will let you have for 7. And then there are the bonuses, where each FFP will reward your status differently, or the 'challenges', where you earn status quickly with AA, and where you reside, or fly from,... sorry but there's just no way to give a definitive, 'better', answer.