Maybe the pages got bigger? On my Windows 7 PC, FF still handles a lot more tabs than Chrome, typically 2x or 3x as many.

Where Firefox falls over is with really heavy pages, such as infinite-scrolling image/gif sites. It's much better than it used to be, but it's still vulnerable.

With Chrome, pages fail to load (giving a blank page) and the Flash plug-in crashes. The browser does stay up, but the effect is the same: you have to restart it.