Foto - Is the 18-200mm going to be your only lens? If yes then the Nikon has no peers imho - If (like me) you want a bit more reach (zoo / ponds / etc) then 200mm isn;t enough & I have the 70-300mmVR which is a cracker also imho
I agree with the f2.8 comments but then you are in very expensive & heavyweight territory ...
HTH - Paul