Hey no problem, I spend stupid money on stuff so you guys dont have to
The plasma's will generally look great with progressive scan dvd players on them, mine is a knockout even for a cheapie. Its really designed to take a progressive scan input from the rgb or component input, with the composite/s-video being poor step-children. Thats why the vb50/n5 trick sidesteps the shortcomings of the cheaper plasmas by prettying up the picture and shooting it through the rgb.
As far as the panasonic goes, they tend to be a step above, but watch out for older plasmas, they tend to run hotter, have lesser lifespans, and many of them have fans in them. Yes...fans...loud as a pc. If you like turning up the volume an extra notch to drown out the humming, its not a problem. My guess is that panasonic at that price point is a first or second generation unit. May be good, may not be.
Program source wise, here's the deal. Good analog cable through a vb50 should look ok on a plasma, but I think if you compared them you'd agree that even a basic tube-based tv will look as good or better, and a rear projection hdtv will look better than that. Good digital cable or satellite on a high resolution channel will look good when piped through a vb50. Note I said "high resolution channel". Most digital cable and satellite providers give best bandwidth to pay per view channels, then to the hbo's, but the local broadcast channels get the short end of the stick. These guys have to supply a lot of local channels so they cant give full bandwidth to each and every one. Hence your "common" channels are going to have short shrift compared to the ones people will pay extra money for.
The plasma is really a 1 trick show. Flat, looks good with high def sources, decent with others. The LCD's similarly offer simplicity and cooler operation, but check them out with a high motion program like a football game, they're often too slow in transition and you'll get shimmering around the motion. RPTV's are big but beautiful and inexpensive by comparison. Of course money solves all problems, as i'm sure folks with a more expensive hdtv will speak well of them, whether plasma, lcd or rptv.
And yeah, when you're input source is less than the unit traditionally displays, AND its stretching it, AND its a bigger overall picture than normal, AND your doubler/scaler/converter has to interpolate the picture by filling it out to a native resolution...the quality has to suffer compared to a 30" direct view set.
If space is a problem, but you can swing a projector, look at some of the 1500-1700 DLP projectors. Many of them only look good with the 15 pin rgb monitor input, buts thats where our $99 vb50 swings into action.
Bottom line: unless you have bucks for this and/or NEED the flat tv dealio, its a huge waste of money.