I have both TVs. I'll be returning the LG this week.
I also already had a P42g25.. But wanted something bigger.
The p50u50 has much better blacks than the LG.
Both screens are VERY reflective. My g25 is much better than these 2.
Input lag... Ugh, the LG has major concerns with input lag. I don't notice any input lag on both of my Panasonic plasmas.
The lg does have more inputs and stuff. The picture settings are more detailed on the LG, but the PQ is better on the Panny.
Much of this stuff most of you already know.. But for those who want to game and play FPS.. Then there is no question you want the Panny.
I wish I had known how bad the input lag was before I bought the LG. Would have saved me the trouble of returning it :/