I'm not clear whether your advocating for Obama or against Clinton. It's true she could have made different choices in her career. Making a decision about whether to vote for her by comparing her career to Obama's is valid. Not voting for her b/c she's a manipulative megalomaniac who somehow tricked Bill Clinton into running for the Presidency in order to set up her campaign is ludicrous. To be fair, I don't think that the previous poster who portrayed her as such meant it literally, but I do think that the point was that Sen. Clinton's ambitiousness makes her seem manipulative. My point is that it's no more manipulative than many men who are successful in politics. For what it's worth, I personally think that someone who decides to run for President after just two years in the Senate is not someone who's dedicated his entire career to helping people, but rather someone with very ambitious personal aspirations toward greatness and power. I also don't think that is a reason not to elect a person, I just think that it's inaccurate to portray Obama as a saint. It's also beside the point to the question of whether people's perception of Hillary Clinton is sexist or not.
The two women you describe as being admirable and ambitious are both in roles that are very much in tune with our cultural ideals of femininity. Of course no one has problems with them...they are not threatening to enter traditionally male-dominated fields. How many powerful female politicians in this country are equally uncontroversial? Not Nancy Pelosi for sure. If people have a problem with the Clintons as a pair, I can respect that. But there is nothing I've ever seen to suggest that anything Senator Clinton has done in her career is any less self-serving than what her husband did.
Also, and I'm trying to figure out where I initially read this (if anyone has a link that'd be great), while Sen. Clinton was on the Wal-Mart board she pushed to decrease the carbon footprint of the chain and Wal-Mart adopted policies that drastically (10% I think) reduced their energy consumption. Of course it's a complicated question to ask what one should make of her membership on the board of a chain that for many is synonymous with evil...but it might also indicate a very different pathway toward effecting change. If you can't beat 'em, join 'em and change them from within.
And just to be clear about where I'm coming from, I'm fairly undecided about this election because honestly I see major flaws with both Clinton and Obama (Edwards is a whole separate issue). But I do think that at the very least both candidates deserve to be examined on their merits. And if there are deep-seated prejudices that are coloring people's views, then those should be examined openly as well.