I think if you are just going by the lenses, you could go either way. Both Canon and Nikon make nice lenses and are very equal to each other. There are also 3rd party lenses that you could use also (Tamron and Sigma) which are very good as well.
I have a Canon 5D and when I was in the process of buying I was looking at the 30D and the D200. We finally decided to go with the 5D because we have prior Canon cameras along with lenses and flash.
If I was starting out and had to decide between the 30D and the D200, it would be the D200 hands down. I really like the features of the D200 and after reading reviews, a lot of people like the D200 also.
If you haven't already, read Steves review of both cameras. (The 30D was just posted).
In addition, here is a review by Popular Photography on the D200.
http://www.popphoto.com/article.asp?...rticle_id=1844
Either way, I think you will be happy with the 30D or the D200.
Dave