$4800 isn't too bad of a deal. Its worth considering. It'll be a decent starter bike for you regardless, and with that few KM's Im sure its just broken in.
The CBR's aren't much different from a ZX6R. I've ridden both (The ninja was an '06 though), and mainly the riding position and some of the characteristics are different.
Both put the power down in much the same manner.
With either, it really comes down to what color scheme & looks you want, since both bikes are quite similar all things considered.
CBR600's depreciate a lot. $5500 is being fairly optimistic, I think if they were to ask your price for it, they'd have buyers. Not at $5500 though, I sure as hell wouldn't pay that for one. Id snatch it up if they'd do $4500 if you can. I assume riding gear is included as well?
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