Firebug vs. Firefox Developer Tools (DevTools)

I remember moving to Chrome. It ran faster than Firefox during the time I was a Ubuntu user. Then I got a Mac and stuck with OSX. I continued to use Chrome but one day, while doing some cross-browser testing, I discovered Firefox's new DevTools. It took a while, but I'm switching to Firefox for my main browser for development to try it out.

But, before I switched to Chrome, it was all about Firefox and Firebug, right!? Well, now that Firefox has it's own set of DevTool, which is better now days?

Firebug or Firefox's built-in DevTools?