good choice, especially since you already have a compatible lens. I too had the same dilemma but the D70 was no where near ready when I was shopping so I went for the 300D. If I were deciding today I would probably lean towards the D70 since I didn't have any equipment already.
The 300D is a great camera and stands very well on its own merit and has an ISO as low as 100 opposed to 200 for the D70
check out this link for an in-depth comparison of the D70 Vs 300D