The Democrats clearly see financial reform as a win-win issue for them -- either they get one or more Republicans to support it, in which case they get an accomplishment, or else they get Republicans to vote it down, in which case they get a great political issue.
But why choose? Chris Dodd says the Senate is going to hold a vote on his bill Wednesday or Thursday. Republicans still say they can muster 41 votes in opposition. The ideal for Democrats would be to have the whole GOP vote to filibuster the bill, then have a huge debate, and then have one or more Republicans defect and pass the bill anyway. Then you get an accomplishment and a chance to expose the GOP as carrying water for Wall Street.