I am comparing several lumix zooms and nikon zooms/primes lately and they both have advantages/disadvantages (Lumix 100-300, Lumix 14-140, Nikon 80-200 f4.5, Nikon 80-200 2.8ED, Nikon 300 4.5ED, Nikon 400 3.5ED). It's not a scientific comparison. Just a thought after shooting with all lenses for a while.

The Nikon AIS with ED glass makes very pretty images. Superior sharpness (and EX tele center sharpness), tonality and bokeh. But focus rings can be a bit stiff and makes the camera shake while focussing. Also the pull/push zooms are not very practical and hard to use with a follow focus. The stiff focus makes the follow focus wheel slip.

The lumix lenses appear sharp due to very contrasty coating with strong colours. The extra contrast seems to demand more from the camera DR in case of the GH2. It appears I get crushed blacks while exposing to the right in more occasions than with the Nikons. Also the extra contrast makes it harder to manual focus with follow focus. If you decrease the contrast in post to match the Nikon the image with levels gamma 1.1, the sharpness looks less. Separating the subject from the background is not as good even at same focal length and aperture. But AF on the lumix is fast and pretty accurate. The app makes you control the GH4 and focus without touching the camera. The lumix 100-300 is just a mediocre lens that produces flat and dull images just too often.

Then the AIS Nikons are not that wide. I also have the Lumix 12-35 for landscapes. I think this lens is ok and I bet it will shine whenever I get my hands on a GH4!