Nvidia pulled a good stunt on the last weeks Analysts presentation. It compared the Pure Video versus ATI's UVD on the high end card.
This was a good stunt as Nvidia compared Intel Core 2 Duo acceleration versus Geforce 8800 GT and HD 2900 XT. The best of all is that Nvidia picked the only ATI's card that doesn’t have the hardware UVD support.
Naturally as you can see below Nvidia wins big time running full H.264 and measuring the CPU load. Nvidia is always between 20 and 30 percent CPU load while ATI takes between 55 and 80 percent of the CPU time.
Core 2 Duo probably running with integrated graphic or with Video acceleration turned of on a graphic card takes between 70 and 100 percent of CPU time. If Nvidia decided to take 2600 and 2400 series of cards that do have support for UVD the situation would change completely.