A local sports photography mentioned that he acquired the new Canon. He described a yellow cast on the 20D's photos when he had it set with the same settings that he used on the 10D. Yes, he can set the new camera to eliminate the cast or do it on a PC.

Can anyone elaborate on the sensors used in these two cameras? Specifically what to watch for when switching digicams?

I have both cameras, I have not noticed any yellow cast. I'm curious what settings were being used by the photog you mention. It sounds like a white balance issue. What his white balance settings are can make a big difference. Custom white balance is always the best withh these cameras, but that makes it very difficult to AB compare the cameras since they have to be compared under exactly the same light conditions. I shoot in RAW usually and a lot of the time set WB to auto, with acceptable results and then tweak the WB in the RAW converter. That said I have yet to notice any casting, it may still be there, I'm not as much of an expert on colors as I'd like to be, but It's not something obvious if it exists.

The best way to find out would be to shoot the same setup with both cameras, in controlled conditions, with both cameras. I'd do it using both auto white balance and a preset. It's possible that the problem is limited to one of that photographer's cameras. No matter how much QA is done, there will always be bad samples and some sample variation.