Mainconcept MPEG Encoder
Mainconcept's MPEG Encoder is a tool used to generate DVD output from source video, be that AVI or Quicktime. For this test, I use a short 2Mbit/sec AVI clip that's been created using a transcoder from a high-bitrate video source, and have MPEG Encoder do some post-filtering and scaling, outputting PAL DVD on the other side. It's multi-threaded and supports HyperThreading.
The Opteron is the very slight winner. The time reported is the time that MPEG Encoder spends on the CPU doing the encoding, rather than a total that includes disk I/O. So while it's possible to say that one of the Xeon's strengths is media encoding, in reality it absolutely depends on the encoder being used.