The Wall Street Journal has a good piece comparing health care plans between Democrats:
Mrs. Clinton charges that Mr. Obama’s plan would leave 15 million people without insurance. Outside experts agree that number is in the ballpark. If people aren’t required by law to buy insurance, many won’t. There are millions of children, for instance, who remain uninsured, even though they qualify for free or subsidized government programs.
In addition, all three candidates want to bar insurance companies from rejecting sick people or charging them more. But it is hard to require companies to insure expensive sick people if they aren’t guaranteed that cheap healthy people will balance them out.
Clinton and Edwards want to require all Americans to buy health insurance. Obama wants to make it affordable enough that everyone has the opportunity to buy. Jonathan Cohn, the health care guru at The New Republic, has more on this.