To be perfectly logical and objective (and to generalise according to likely proportions), MTFs were raised as men, which entails to notably defend your point vividly and to basically walk on whoever disagrees. It's also likely to have left a profound trace of aggressivity on many of us, because that's how both education and testosterone showed us to settle things.
On the other hand, FTMs were raised as women, which entails to be understanding and soft. It could also have left some sort of "inferiority reflex"/shyness when sexism remained in the education (which is sadly pretty often). Moreover, years of having a body dominated by oestrogens could have taught the person to reason and feel before acting and talking.
There's also another thing. Today's society, but to a much greater extent, the historical "feminist boom" is telling women to be assertive and fight for themselves, as a reaction to past and present oppression. MTFs, especially previously conditioned by that "manly" history of theirs, could have taken those teachings to heart.
