Regardless of which camera you get, be sure to get the fastest CF card you can, you'll get better overall performance.

This will make a big difference on the Canon D-Rebel, since it has a relatively small image buffer. It's less necessary for the Nikon D70. I have two cards, a "16x" Lexar 1GB and a Sandisk "Extreme" 1GB. The Sandisk is supposed to be one of the fastest you can buy, while the Lexar is an older generation card. Honestly, shooting with either card, I've never noticed a difference, and I've gotten into the press photographer style of shooting several shots in rapid succession to make sure at least one comes out right. The D70's buffering is good enough to hide the slower throughput of my Lexar card.

When in doubt, check out Rob Galbraith's database. He measures the throughput of every different card against every different camera and discusses whether you need faster cards or not.