Ask HN: Wireframing - How should I wireframe?

I was having a discussion with my designer friend about how to go about wireframing a site.

I was under the impression that if you have the skills to do so, using a framework such as twitter bootstrap and creating code would be a lot more efficient/lean than using a program such as omnigraffle to first wireframe through images, and then again create a prototype/wireframe in html.

What is the benefit of using the Omnigraffle -> Bootstrap Wireframe -> Dev

Vs.

Bootstrap Wireframe -> Dev

Thanks!