What´s best practice to responsive design? Use % or em and rem?

问题

What´s best practice for layout responsive?, I read some articles that´s recommend use em and rem´s for layout, foundation 5 for example use this practice.

What do you think?

来源：https://stackoverflow.com/questions/27265868/what%c2%b4s-best-practice-to-responsive-design-use-or-em-and-rem