Difficult to answer that in a sensible way,i had no complaints about it at all,its a lot cheaper and you can see the results in this thread,the Nikon has a slightly longer zoom but nothing really to shout about,the one thing the Nikon has that i like is the button on the side of the lens that knocks the zoom back if you lose framing,you can then re frame and let the button go and the lens jumps back to the previous setting.
If i give it serious thought the main reason i bought the nikon is my enjoyment of this forum and my desire to post any pictures i want anywhere on the forum,i never watch TV so its taking pictures, PP or surfing for me,so i cant give you a good reason to buy the Nikon over the Panasonic.
I used a canon with that feature to press a button to zoom out to find the subject, it was very handy.
My problem is I need something longer than my 70-300mm but my main option for the D7100 are going to take some time to save for.
Last night I went to see some short eared owls with a friend but they never came close enough for me and my 70-300mm.
This is my best shot sooc taken at 250mm (where the lens is sharper) in 1.3X crop mode so I think that works out at an effective focal length of 500mm and 15.6mp image with the D7100, correct me if I'm wrong.
This is a cropped and slightly edited version from the same series. I think this works out at about 2.8mp.
I assume that under the same conditions, static bird and using car as a support (light wasn't that good but ok), I would have been able to get a much better result using either of the bridge cameras you have been using? I struggle to envision the size of the owl in the frame at 1200mm but it must be quite a lot bigger whilst retaining the full 16mp of the sensor.
If I can spend £200-300 and get decent images that are out of my current reach, that might help my patience saving for a 300m prime or similar. I'd probably carry both the bridge and D7100 so when things are close I can still take advantage the superior D7100.
Sorry for rambling