World wide Audio Visual experts all agree that the Pioneer Kuro Plasma is the best flat screen panel money can buy - LCD or Plasma.
LCD screens are good for daytime viewing in bright environments, but at night can be too bright and therefore never correctly display dark scenes, and lose detail in blacks.
Plasma screens run hotter, consume more electricity, but overall handle fast moving video much better. Because the plasma screen is glass, they can be difficult to watch during the day due to reflections from windows.
Bluray will be fine on both, assuming that each panel is capable of displaying HD video.
PS3 or Xbox360 will be fine on both - some plasmas can be affected by 'image retention', but some LCDs can suffer from image lag on fast moving games.
You also get more value for your dollar with a Plasma for the same screen size.
But the key to the whole debate will rely on the source of video you feed into the display. Hook up your old VHS and you will never get a decent image at 40"+. Even SD DVD can look quite 'blocky' if you sit too close to a big screen. HD FTA can look good, but the quality can vary between programs. Make sure you always conect your devices via HDMI or component (not composite). Foxtel is known to look very average on even the best of screens.