Fuji would have a bigger dynamic range for sure, it uses Nikon accessories such as flash and lenses, and is weather sealed. It has a 1.5x crop factor and is cheaper at $1899. At full dynamic range, it's files are bigger than the Canon and I'm almost sure the camera will be slower as well. Since the body is from the Nikon D200, I think it feels nicer than the Canon.
It's an interesting proposition. Many wedding photogs prefer the Fuji to Canon or Nikon. My neighbor at work who is a professional used to shoot with a Fuji s3 and a Nikon D200, once he heard about the upcoming S5, he sold the D200 and put an order for a S5 and is currently shooting with a borrowed s3 as a back up. It should come out in Feb. I'd wait for a test at dpreview before making any judgments about IQ compared to the 5D.
As for when the Digic III will come out and if it will have a wider DR, your guess is as good as anyone's.