I think you know my history of D70S user upgrading to D80 and have seen some of my D80 work ( a few shots here but mostly on "the other" site.)
I thought about the D200 and, if I had the money, would probably go for one. That was until I decided I wanted a second body. ( the D70S was originally going to be my second body when I bought the D80). I sold the D70S as a kit with a couple of lenses, CF cards and bag for £500 to fund the purchase of a second D80 body. I got that for £529 at Jessops who, at the time, were offering to match any published price in Digital Photography magazine.
The first D80 was bought last September at Gatwick Dixons, tax free as a kit with 18 - 70 and a 2 gb Sandisk Ultra 2 for around £700. SD
memory was quite a bit more expensive then than it is now.
I therefore now have 2 x D80's, Nikon 18 - 70, Nikon 70 - 300 G, and a Sigma 170 - 500 for a total cost of £1,623. The 70-300 and the Sigma were admittedly bought second hand mint condition on Ebay for £80 and £285 each respectively. I bought the second body in order to have the ability to have two different lenses set up ready to use without having to do a quick change and incidentally avoiding the influx of dust.
Its also worth noting that I paid a total of £16 for a genuine ENEL3e battery from Hong Kong, postage paid and no import duty. I bought just one initially to test the delivery and tax implications, I'll be going back for more.
2x D200's, body only would cost £823 each (current Microglobe price), twice the price of my current total kit.
That explains the cost implications, what about performance ?
Well, I can't compare one to the other as I've never used a D200. I do know that the 10.2 mp sensor is common to both, that the D80 has 3 fps motor against 5 fps for the D200 and that the D80 uses sd cards against CF cards. As others have said though, you can get memory very cheap these days.
I'm very happy with the D80. It's a distinct upgrade from the D70 series, I find it quite robust for my use ( and I'm known for being a bit ham-fisted at times ) and I found it easy to adapt to from the D70 with the control layout and feature uses much the same as the D70.
What you probably need to do is go out and find a pro camera shop willing to let you spend more than a few minutes handling the two cameras and then make your decision based on cost against handling and features. Whichever you eventually settle on, you won't be sorry.