Panasonic - Makes the complete units, Supplies Toshiba, JVC, Fujitsu and more

Sony do not actually make Plasma's they use Fujitsu/ Hitachi screens

Pioneer owns NEC and has switched production to the NEC lines. The new 50 inch and the 42 inch units are all NEC glass. To tell if a 50 inch is Pioneer or NEC, check the resolution, If 1280 it is Pioneer , If 1365 it is NEC . 42 inch Pioneer Plasma TV is NEC

Philips - Uses Fujitsu/ Hitachi glass screen and most internal components

LG / Zenith - Make their own glass in Korea
Samsung - Makes its own components in Korea

Toshiba- OEM from Panasonic

I would choose Panasonic all the way, these are the best units bar none imho