The look of the two is completely different, so you really need to go see for yourself (at some place that knows what they're doing with regard to HDTV and plasma - - not at your local Good Guys) The plasma, even with standard TV shows NO scanning lines and NO flicker. Graphics and such are rock-solid. They truly look like they've been painted on the screen. It's like watching a flat panel computer display vs. a TV set.
I used to have a Pioneer RPTV, and after six months with the 42" Panny, I could never go back.
Major disadvantages of RPTV: a) The narrow viewing angle and generally uneven brightness level b) constant fiddling with convergence and such to get a perfect picture (plasma is pretty much plug n play) c) all the space it takes on the floor and the resulting high WRF.
Disadvantages of plasma: a) Cost b) more complex hookup. A plasma is just a monitor, so there's no way to watch it without also turing on at least some other gear (e.g. a set top box or DVD player) That's also true of RPTVs in a home theater, but those also have a built-in tuner, so the wife can just push one button and "watch TV." (Mine can too, but it triggers a macro that powers-up and configures three boxes.)
Against this, you get a fabulous picture, viewed from any angle, even in a brightly-lit room. You also get a very big friends-and-neighbors Wow factor when they see your TV picture hanging on the wall. If you go to Japan or talk to people in the industry, it's clear that all large-screen TV will be plasma within a few years. An RPTV you buy today is going to seem like an antique pretty soon.