In reply to Bryan Hoffman.

I'd say the only advantage ACF has over CMB is flexible fields: http://www.advancedcustomfields.com/resources/flexible-content/ (2:50 mark is where you see it in action).

If a project didn't require that, I'd go with CMB every time, hands-down. The ability to define fields in code is priceless, and the CMB addons go a long way.