Don't choose the one you think you "ought to" get. Forget the tech specs - the differences between the two cameras won't be noticeable to a beginning DSLR user. In any case, once you start to be truly impacted by the limitations of these cameras, you won't be wishing for the other brand's entry level model. You'll be wishing for the 40D or the D300.
Just choose the one that you intuitively feel you can live with well enough to pick it up and fire it 30-40,000 times in the next twelve months.