Quick (and simple) comparison video between the Sony E-mount 18-200mm f/3.5-6.3 OSS and the AF-S DX Nikkor 18-200mm f/3.5-5.6G ED VR II on the Sony FS100. The Nikon lens was placed on the NEX-FS100 with a Novoflex adapter. No camera or color settings were changed between shots, only the lenses.
These lenses are very similar in performance, more then I expected it to be.
The Nikon 18-200 VR II or VR I is a well known lens in the photography world so at first, I expected it to perform better then the Sony lens. I prefer the Nikon lens over the Sony to work with, because of the focus ring with true stops and markings. With the Novoflex adapter you can adjust the iris manual and easier then with the small dial on the camera. Also zooming in with the Nikon lens goes a lot smoother. The Sony lens on the other hand has image stabilization and auto iris / focus for fast shooting when you need it. So unfortunately there is no simple answer to the question "Which lens is better?". They both have things going for it!
In short: I prefer working with the Nikon lens over the Sony lens, when there's more time to setup my shots. And I prefer the Sony lens over the Nikon lens when there's less shooting time (for Run and Gun work). Further more, I would have no problem editing shots of both lenses together in a single project. Actually, it would be rather difficult to tell them apart.