if yur a semi pro-- you would know about the market methinks ... afterall your paycheck depends on it.
Canon 20d if you got the cash for the body and have enough for decent glass ($$$) or the nikon d70s (still nice body, but a few hundred less than the 20d= more money for glass... Of course, if your looking to move into the "pro" ranks, the new D2s nikon at around 5k is awesome.
Usually experienced folks buy the brand that they have a stockpile of expensive glass for already.... Nikon folks stick with nikon, canon=canon...
I have the D70 for serious shooting and a canon sd500 for point and shoot. Both are superb for their intended use.