I would recommend Samsung over lg. and unfortunately those are your only two options.
the Samsung f8500, is the last 'high end' plasma that will be on the market. it is without competition currently. the 5-series from Samsung is probably the next best option if you aren't looking for the best
I've never seen a tv with undefeatable FI, that's a weird move on LG's part if that's true. but I'd be less surprised if they just told you the wrong information. either way, it's definitely defeatable on the samsungs
Displays: Samsung PN64F8500/JVC X35
AVR: Pioneer VSX-1130K, 7.1/5.1.2 audio
Sources: HTPC(Enby), PS3, XBOX360, Wii
Control: Harmony One