Robert Parry makes the case that Obama is less vulnerable to right wing attacks than Hillary: 

What Sen. Obama didn’t say out loud, but what Democratic voters
surely recalled was the endless baiting of John Kerry for having been
“for the war before he was against it,” earning a place – as George W.
Bush put it – “in the flip-flop hall of fame.”
 
Hillary Clinton would be open to similar attacks since she voted in
2002 to give Bush the authority to invade Iraq and remained a staunch
war supporter almost until the eve of Campaign 2008, when she realigned
herself with the anti-war sentiments of rank-and-file Democrats.

She was for it, for it and for it – before she was finally against it.
 
But another factor that plays to Obama’s advantage as the prospective
nominee – when compared to Hillary Clinton – is that the Right’s
powerful media apparatus and the Republican attack strategies appear
less successful against Democrats with strong oratorical skills and the
ability to inspire enthusiasm and passion.  Read more.

The point is that if you are a stilted and ineffective
communicator, you are easily made into a screen onto which the
opposition can project the distorted image it wants the public to see. But if
you radiate your own light, the image projected onto you is obliterated
by your own self-defining fire. Obama will effectively resist being defined by the right as long as he burns with that cool blue flame which is the special quality that distinguishes him from the other candidates.

Hillary’s not bad as a communicator–she’s clear and fluent–but she’s not Bill. And by her own admission, she’s prose to Obama’s poetry.  She’s a dull flourescent tube in bleak government office when contrasted to Obama’s steady, burning flame.

P.S. Parry also outlines other Hillary vulnerabilities  that relate to Bill’s business dealings since leaving office.  Even if there’s nothing there, they will be exploited to  aggravate the "Bill problem" for those who are uncomfortable about the prospect of a co-presidency.

P.P.S.  Here’s a repost of a comment I made under the "Cool Debate" post earlier this week about Obama’s vulnerabilities:

No question in my mind that the GOP will get nasty in the ugliest
kind of racist way. Won’t be McCain of course, but some group he has no
control over. So yes, I do think Obama is vulnerable there.

The question I don’t know the answer to is how many Americans will
be affected by those techniques and to what degree the Democrats have
wised up about how to defend themselves against those kinds of attacks.

Obama isn’t stupid. You know his camp has got to be preparing for
the swiftboating this time around, and he’s done well so far in
parrying the, admittedly, mild attacks directed toward him by the
Clintons. But, sure, Obama’s vulnerabilities worry me.

The dittoheads are a lost cause no matter what, but what I want to
believe is that most Americans–enough, at least to matter in an
election–see these techniques for what they are. I think there is a
general disgust with Republicans that the Democrats can work with to
repel this kind of attack. We’ll see, but that’s my hope.

I also think that Obama will get more sympathetic treatment in the
media than Clinton will. Because you know all the anti-Clinton rage is
going to come out again. New angles on Vince Foster, Whitewater,
Monica, lesbian feminazism, etc. It doesn’t matter that we’ve been
there done that. What matters is how it plays in the media, and the
media is obsessively politically correct when it comes to race, and
obsessively vicious and unfair when it comes to the Clintons.

I think McCain wins the media perception battle with Hillary, but
he’ll lose it with Obama. I could be wrong about that, but that’s the
way it looks to me now. Romney loses against both.

If Obama can’t win the foreign policy debate with McCain, then I’m
completely misreading the war-weary public mood. Americans are not
particularly sophisticated, but they’re not dumb enough to buy McCain’s
pro-war stupidity at this point in the game. The war-without-end stuff
he’s been saying is ridiculous and should be easy to make fun of
and exploit. The age vs. youth thing–I think it could be argued that
it works in Obama’s favor. Obama looks and acts presidential. He’s not
an empty suit like John Kerry. I think he wins the foreign policy
contest easily.

The picture will become clearer as we go forward. There are layers
of factors, and you can’t discount the surprise factor. But for now, I
feel comfortable in saying that both Obama and Clinton are equally
vulnerable and both are tough enough to deal with the mudslide when it
comes.