"DivX rep Ryan Taylor told me that his company's video decoding technology is just better, which means devices running it can do more video with less horsepower, leading to better-looking movies, better battery life, and cooler laps," according to CNET. "The HiQ product can also use the graphics processor of the computer it's running on, to put the video decoding on the chip best designed to do it."
This is good news: competition in the video player space on the Web will surely yield a better experience for users. Still, it's hard to say at this point if users with netbooks or slower systems will want to install DivX HiQ to get a performance boost, but right now we don't recommend doing so as it's still in beta anyway.
Adobe Flash 10.2 entered beta last week. 10.2 introduces Stage Video, a new API that delivers high performance video playback across platforms, and IE9 hardware acceleration support. DivX says its video playback is still more processor-efficient than the Flash 10.2 beta.
Until the two are out of beta, it's not a good idea to mark either of them as the winner. Even then, we would not be surprised if both plug-ins performed differently on various systems. Either way, regardless of what you end up using, it seems that you're going to get some sort of performance boost.