The D70 has a different type of shutter. Practically no one uses it any more. Longevity was an issue apparently.
As to why the D600 has a 1/200 shutter when most other models are 1/250, I cannot say other than it was probably a cost saving feature. I grew up with 1/60 or 1/125 synch speeds, so it's all great to me!
>I'm wondering if anyone has an idea as to why Nikon made the >D600 with an X-synch of 1/200, versus the 1/250 of nearly >every other DSLR they made, or the 1/500 of the D70? It seems >a step backwards without any discernible reason as to why. > >(yes, I know a lot of other brands synch at slower speeds, but >I'm wondering why Nikon went backwards)