justleesa, it sounds like you have no "investment" in a brand; for most that settles the question: "I already have these Canon lenses, so it's cheaper to stick with Canon".
Generally, Nikon vs Canon from scratch is a wash. The high-end lenses are both great. The bodies have similar feature sets. Prices are similar. Not an easy choice, is it?
At this point, the conventional wisdom is to pick an aspect of your shooting that stands out, find the best performer, and grow from there. As an example, the Nikon D70 has great write speed to the card; if you're shooting sports, this might be important to you. Voila, you're a Nikon gal.
The other aspect (usually not discussed) is the future. Nikon has frozen their digital format and chip dimensions, so all future equipment will expand on this. The selection of compatable lenses and bodies will grow in a standardized way. Although the chip pixel counts are smaller (now), it's inevetable that it will grow.
Canon has a split in chip sizes; some similar to the Nikon, others 35mm in size. This is great for the 35mm film shooter that wants to lateral into digital, but lenses and equipment are schizophrenic from having to fulfill two formats. If buying for the long-term investment in equipment, this might worry me.
Having said that, they are both excellent lines. Perhaps a coin flip would be best....
My counsel has alway been to start at the optics. Pick the lens and port that you'd shoot the most, and the quality level you want, and the rest will fall in place.
All the best, James