The Panasonic ET5 is alone among Pannys in that it, like the LG, has passive 3D. The Samsung is active 3D. Passive has better 3D to the extent that there is less ghosting and flickering and the glasses are dirt cheap (free if you keep the ones you get at the movie theater) but resolution in 3D mode is lower than is the case with active 3D. Samsung's active 3D glasses are cheap relative to other makes' active glasses (about $16 a pair.) Samsung's current model active sets are among the better performers vs other makes of active set.
The LG and Panasonic sets you list use an IPS panel which gives better off angle performance (less color fade and loss of black level when viewed from the side vs straight on) than the Samsung, but the Samsung when viewed straight on has a bit better black levels. Any edge lit led (all three of those you list) is somewhat prone to flashlight effect from the edges of the screen during dark scenes. Samsungs are among the worst in this respect.
The better straight on black levels on the Samsung will be of benefit primarily in a dark or very dimly lit room, but this is also when flashlighting will be most obvious. If your room isn't going to be really dark most of the time and you want really effective 3D with minimal ghosting etc. go either the Panny or the LG, whichever's cheaper.
