rational self interest and feminism

I'd like to draw some parallels between the points raised by Hum (Hum's Pol Philling) and Chris (words unto chris).

Chris asks about what counts as "rational self interest" and wonders whether it can really be as contentless as Rawls seems to think. If we don't know anything about our (personal or public) position in society, as the Original Position requires, what remains of self-interest? Conversely, doesn't self-interest (rational or otherwise) actually operate from a substantial basis - such as which neighbourhood group we belong to, in Chris' example? What is self-interest, exactly, and what is its political significance?

Hum asks some similar questions in relation to difference feminism. Should feminism be about regarding and treating everyone as equal, and therefore the same (a bit like the way Rawls sees everyone as the same in the Original Position)? Or should it at equality by recognising, but trying to overcome differences (as in the positive discrimination in employment example)? Or should it be about recognising and affirming, even celebrating at least some of the differences between people, especially between men and women? Another way of asking these questions might be to wonder if "rational self-interest" is the same for men and women...