The reason I think the difference is worth it is contrast, blacks, and color saturation are noticeable at all times, no matter what the distance. To me, it's worth the extra $1000 for the Pioneer. Yet the extra resolution was not worth it, especially since I normally sit 10 feet away. Why pay for something you will not ever see? On top of that, the Pio's have 4 HDMI inputs, while the Panasonics have 2 (another thing is the component video on Panny's is only 720p, and I have an old xbox without HDMI, so no benefit with 1080p the xbox where I normally sit closer). I think the big thing is I am a huge CRT guy due to color and blacks, and the Pio's are the only ones that even touch CRTs in that aspect.
I am not shooting down anyone that paid extra for the resolution. If you think it is worth it, go for it. Yet don't pay the extra just because it sounds better.
To me, it was the Panny 700U or the Pio 5080HD. Better res or better overall picture. I went Pio. I think many others need to do the same in their price class. If you are in the $1800 price range, do not ignore the Panny plasmas due to lower res. The pictures on the Panny's are really nice. I didn't do the comparison in that price class. Yet don't shoot down a tv on resolution alone. It's is no where near as important as contrast, processing, color saturation, color accuracy, etc. In the end, get the one you think looks better no matter what the resolution, and do comparisons from your normal seating distance.