Nope, I mean you can compare anything with anything if you want, I dont know why 40d d300 comparisons keep cropping up apart from just general interest, in a fight to the death nobody without brand loyalty would choose a 40d in a rumble with d300, I dont think its fair on the 40d, its not even a pro body.
30/40d is d80/200 territory.
It wont do either manufacturer any good to place their products in direct competition, because the choice would be simply one or the other and lead to a cut throat price war, so all models are carefully placed.
The D300 is much closer to a 5d than 40d and indeed surpasses it in many respects, but its not exactly like for like.
Its pretty clear what D3's target is, but again not exactly like for like.
Make no mistake the D300 has totally knackered Canons product placement game plan, they need to get a new 5d out or something because at the moment unless your heart is set on fullframe, d300 is the better choice....an un-partizan choice.
I am partizan, but I'm not blind
D40/D40X+D60 v 400D/450D
D80/D200 v 30D/40D
D300 v 5D & maybe one of the earlier D's, depends on the features important to you.
D3 v ....depends on the features important to you.
non exactly like for like but as close as it gets.