If you are really a "videophile" and you want an accurate and realistic picture, you should definitely get the panny g25. Also, black level is better with g25. However, if you just like tv and movies but don't scrutinize the accuracy of colors and such, the samsung will be great, especially 300 bucks cheaper. Overall, I'd say that samsung's in general have a nice and punchy presentation, and they also look quite sharp. Unless you are a stickler and super critical, you'll be quite happy with both.
I'm almost ready to pull the trigger on a plasma and I'm almost 100 percent sure that the g25 is the one. Good luck and have fun with your decision!