I'm one of those guys that has been saying that the comparisons aren't quite appropriate.
Basically two reasons why I believe this.
1) The 20D is Canon's replacement for the prosumer 10D. It is higher priced and certainly has many features that make it more desirable than the lower priced D70. It is aimed at the serious amateurs/professional wannabees/semiprofessional group. Nikons equivalent (which is sadly not very equivalent) is supposed to be the D100, which is long over due for replacement.
2) That being said, the D70 is supposed to be an entry level consumer DSLR aimed squarely at unseating Canon's entry level digital Rebel, and is priced closer to that camera.
However, in terms of actual performance, the D70 measures up quite well against cameras destined for higher performance markets, including the 10D and 20D (remember that this is still a fairly new product) and is definitely a step up on the digiRebel imho.
I've played some with the 20D, and it is one awesome camera, right up there with my 1D Mk II in terms of outright speed and performance, and on a par for image quality at a fraction of the price. About the only thing you're giving up is the tank like build of the 1D.
You really cannot go wrong with the 20D. My wedding photographer told me when I got started 15 years ago, to get the best I can afford because in the end I'll spend more on film and lab costs than on the equipment, so why buy something I'll outgrow, right? It's not quite true today, but it still has some merit in principle. You will be hard pressed to outgrow either of these cameras. I know that doesn't really help you, but I thought I might elaborate on the apples and oranges comparison.
p.s. Go for the 20D ;)