Should CMOs be Batman or Robin?

I read two posts last week that got me thinking about superheroes and sidekicks. One was by Rob Enderle entitled  HP’s Hurd, Dunn and Fiorina Could Learn from Superheroes. The other was on AdAge.com by Jack Neff entitled Meet the New and Evolved CMO Rock Stars.

As I’ve been interviewing CMOs for my upcoming book, I’ve met some very talented leaders who go about their roles in very different ways. Some view their roles as supporting their CEOs and bringing about the vision that their bosses have set forth. Others are the lead change agents for their brands and find themselves (comfortably) in the spotlight as they share their plans.

So my question for you is, should CMOs be Batman or Robin? Or is there a better tandem to use as a model for CEO/CMO partnering?