I don't have a D3, I do have two F3s and I do have an EOS 5D which has roughly the same MP as a D3.
I also know that in my hands, the printed results from my 5D are far superior to anything I've printed from a scanned slide, but then I don't have one of those "dedicated to 35mm" scanners.

(I've just had a quick look at the review of the R2400 and it looks as though the reviewer was well satisfied. But where will you find one to test?)