Neil Irwin breaks down Yellen vs. Summers: Who would be a better Fed chair?.
I'm not really sure. From what I've read lately, Summers was during the crisis more for stimulus than we initially thought. Yellen is certainly qualified and policies will be like Bernanke's. My understanding is that the Fed chairperson is the head of a voting body and has to convince other fed chairs to vote for policies. I have no idea if Yellen's quieter or Summer's abrasive demeanor is more likely to be able to get votes for more stimulus.