Hmm, so do Chrome and Firefox use GPU acceleration or CPU acceleration then? I'd assume the latter, because I do have an external GPU after all, but I'm just not too sure -_-
But yes, HTML5 in IE is also smooth, and I'll continue to watch Youtube videos in IE until Chrome allows for less CPU usage with flash content.
Both Google Chrome and Mozilla Firefox also use varying amounts of GPU acceleration, depending on the operating system, graphics hardware, and graphics hardware driver. Most GPUs, be it integrated or external, should be able to handle GPU acceleration with aplomb. Heck, your
smartphone is probably doing it provided that it's using a semi-recent mobile browser. As long as the GPU isn't way too ancient (think before DirectX
9 and doesn't have a bad driver), it'll automatically accelerate web content as long as you didn't disable it yourself.
Google Chrome doesn't accelerate much on Windows PCs, though, when it comes to general web content (2D Canvas and WebGL are another thing). Firefox should do it the same way as IE does on Windows Vista and newer, utilizing Direct2D on supported hardware, and hopefully can achieve parity with regard to performance.
The fun thing about GPU acceleration is that browsers
do have to have a CPU fall-back just in case the GPU is unusable. GPU accelerated browsing can be finicky since GPUs aren't exactly designed to display web content - they usually operate on complex 3D scenes. Chrome and Firefox fall back to GDI+-based rendering (not accelerated at all since Vista; although it's accelerated in XP, it's going to be slower than Direct3D or Direct2D), while IE uses WARP (a software DirectX 10+ rasterizer, effectively providing a "GPU" without a compatible GPU).
You probably won't notice GPU acceleration unless you have a relatively slow CPU. That's when the benefits of GPU acceleration work its magic - even slow, out-of-date single core smartphones can handle desktop sites just fine as long as it's not running out of video and/or system memory.
Google Chrome uses its own Flash player; sometimes, this Flash player can get buggy.