I've been testing out various distros since 1998, and that's been my experience all the way back: to run at the same clip as the concurrent Windows, linux (at least with the desktops of equivalent competence and featureset) needs about 3x the hardware under it.
Clip? What clip?
Are you referring to some internet video played using Flash? Flash under Linux is about as crappy as Flash under OSX. Officially Flash under Linux supports some form of video acceleration but I never saw it work properly. Luckily the world is moving to HTML5 video.
For a while AMD tried pushing their own video acceleration technology under Linux. AFAIK nothing noteworthy ever supported that. Luckily at least their open source drivers started supporting VDPAU, originally invented by NVidia. AMD's proprietary Catalyst drivers do not support VDPAU natively and require a small wrapper library.