I started with the Panny as I had the older 3000.
Fantastic picture, excellent zoom memory.
After reading the reviews it was the one for me.
3D....awful, crosstalk everywhere. I went back to the retailer, we fired it up against their demo unit, both the same, loads of crosstalk on most titles.
JVC X30 - heavier, larger, quieter, better 3D (despite what the reviews say, 3 of us in the demo room all thought the same), brighter and sharp as hell.....wow
It took me a few days to get used to the sharpness as it doesn't look as smooth as the Panny.
The Panny had faster zoom memory but for all the time it takes I can live with JVC's first attempt (and you can zoom whole watching source).
I am picky but when you are spending £3k you want to get it right.
My only worry is bulb life, but with a year warranty I'm hoping all will go well.
You won't be disappointed with the Panny in 2D but if you are buying it because of better 3D please demo, the JVC in 2D is amazing, thankfully my dealer let me swap at no cost!