Hello. I've been looking pretty hard at the 720p version of both of these units, trying to decide which based on cost, reviews, etc.
Last night I want to Circuit City and Best Buy for several hours, these are the only places near me that have both units, and luckily they were side by side with each other, as were the 1080p units that you are looking at.
First thing was to find my way around in the basic menus of both televisions. Samsung unit had more features in the picture menu than the panasonic. I proceeded to set color, brightness, contrast, and cell light values to the same number on both units. Then I assumed a position about 10 feet away for about 2 hours watching those stupid loops they have playing.
I did notice that the Panasonic had a darker black tone to the picture than did the samsung. To me the color and clarity was better on the Samsung picture.
One example that really stands out in my mind, was during one of the Directv football ads, Jimmy Kimmel was standing in front of an unilluminated scoreboard. On the Samsung I could see the individual light bulbs on the score board and on the Panasonic the image sort of ran together like a solid black wall.
Then there was a nature loop in which I just felt like the Samsung had more clarity and color accuracy for my tastes while looking at rocks, water, flowers, etc. The Panasonic seemed to have color hues (green, blue, or red) on different scenes while the Samsung just seemed more natural to me. Also I liked the skin tones coloration on people better on the Samsung. I noticed that the Panasonic made everyone look sort of pale while the samsung gave people a more orange tint like the makeup they wear.
Overall I think I have decided to go with the 50" 720p Samsung plasma. I just don't see a need to spend an extra $500+ for a 1080p unit. It might be a little cleaner on 1080p source if you have them side-by-side but I don't think it will be much. Plus Frys.com has the 720p Samsung for $999 right now and I'm ready to upgrade my TV right away after spending so much time looking.
In summary, I would just go to a store on a weeknight when crowds are minimal, familiarize yourself with the picture menus, and adjust the settings to more practical values on each tv and see what you like best. Spend some time comparing the images and see what suits your tastes better. If the same thing was the best for everyone there'd be no competition. Don't just buy something because so-and-so says it's the best, especially something that is as subjective as vision.
I am buying one of the two set this week end I would really appreciate you're input on which one is better.