Well im not sure how well read up you are on the different models and also the common gripes with Samsung plasmas..
Samsung plasmas, especially the mid to low end models tend to have a problem with a buzzing sound coming from the panel.
Panasonic plasmas have been considered the best plasmas since Pioneer left the game.
Honestly I would go with whatever you feel you want. Im not brand loyal by any means, but I would rather get the Panny (despite rising black levels) than take the chance and get a Samsung set that has a buzzing issue.
imo, hope that helps at all. If you want to do some research, head over to avsforums.com.
And the Panasonics have rising black levels. LG has a lousy picture compared to Samsung and Panasonic. Sylvania LCDs are entirely powered by little artesians that die if you don't feed them daily, too.
But in all truth, plasma is a fairly mature television technology. It is literally difficult to purchase a bad plasma tv from Samsung or Panasonic. Glare and the list of features are the only real concern for the average consumer when it comes to plasma televisions. If you get a bad one, take it back and exchange it.
I know three people (besides myself) that have Samsung plasmas that were purchased in the last 24 months (two PNXXB550s, a PN50A450 and a PNXXB850). None of them have a buzz that's audible past about 12 inches. I know two people that have Panasonic plasmas that were purchased in the last 3 years. None of them have black level problems that are noticeable to the normal viewer.
My point being, every manufacturer puts out a bad set once in awhile. It shouldn't be strange that the same problems crop up from the same manufacturer. They are rare. Everybody complains when there is a problem, but they rarely speak up when it works as advertised. I don't know
anyone that has had an unexpected problem with their HDTV in the last five years (DLP,plasma,LCD,whatever).
If you are 13 feet away from the tv, you won't notice the difference between 720p and 1080p unless you use it for a computer monitor. From that distance, the pixel size of a 42" plasma won't make a lick of difference either. I'm willing to bet that from 13 feet, 998 out of 1000 people couldn't tell the difference betweeen 720p and 1080p on a 50" plasma. Odds are that if someone is asking whether to get 720p or 1080p, they'll be one of the majority that won't be able to tell the difference. In fact, since Blu-Ray is almost the only mainstream way to get true 1080p, it's a moot point the majority of the time anyway.
Sorry to rant. I know the discussion is half the fun. I'm certain OP will be happy regardless of which tv he/she purchases. Just get the one that does what you want and looks good while doing it.