Having experienced my friend's D70s... it appears that the Auto White Balance is not that accurate. A lot of my friend's photos have a yellow tinge for pictures shot under artificial light. Even when we tried all the manual WB settings, all the pics appear with a yellowish tinge.
Using my 350D, I get really nice accurate colours on AWB. I hardly have to change that. Add the fact that you have 2 more megapixels (extra MPs are always better than less) and a CMOS sensor (with better noise control) means that I would recommend the 350D over the D50.