When it comes to SLR's I have always been a fan of Nikon.
With that said....
The Canon 20D blows the Nikon D70 out of the water. In fact......Canon Digital SLR's in general perform better than Nikon and dollar for dollar are more cost effective.
The Canon's focus faster, have better battery life, and cost a bit less especially when it comes to the accessories.
Another note.....I own the Canon 20D and I shoot the majority of my images in "portrait" rather than "landscape." This means that more often then not, I have the camera turned sideways. Although this may seem trivial to a lot of people...It's important to me that I was able to add the optional battey grip to the Canon. Not only can I shoot for a lot longer but the batter grip includes another shutter release button for use when the camera is turned sideways.
The D70 does not offer this option.
