well since u want a 40inch tv and ur viewing distance is 5 to 6 feet u will need a FULL HD tv,since plasma like pansonic have a resolution of 1024x768.to make u understand,simple rule for HD tv to come in the first place is more resolution the better,but at a certain point humans will not be able to see the advantage of more pixels,but with 40 inch and above lcds u definetly want more pixels especialy at ur viewing distance.if a tv has lower resolution u can compensate by increasing ur viewing distance.
now take for eg if u take a regular 29inch crt tv ,now if u see its pixel density u will notice approx 815 pixels/per square inch, now when u take a 42inch plasma like TH-42PV80H it will have approx 1044 pixels/per sq inch . but when u take a 40inch HD lcd it will have 1535 pixels/ sq inch, so it has roughly about 50% more pixels / sq inch then a plasma,and a FULL HD 40inch lcd will have approx 3035 pixels / sq inch which twice that of a regular lcd and 3 times more then a panasonic TH-42PV80H .
so tell me which would be better. the panasonic plasma produces a contrast of around 1800:1 where the sony and samsung lcd produce a contrast of around 2300 to 2500 which is more then the panasonic plasma.
so i suggest u get a lcd like the samsung series 5,or if u happen to buy in the grey market get urself a samsung series 6 or ask for series 7.do note samsung will soon officialy launch series 7,8 lcds in india.