Plasma TVs have better contrast than LCD, if you want LCD look for the highest contrast ratio.
LCD tend to use more power
LCD tend to also eat their own PSU (Phillips and LG)
Pioneer and Panasonic are just about the best brand leaders
3D TV and OLED TV is just around the corner.
Thats off the top of my head and now maybe old news but I used to work in the industry where good panel displays were important.
My own low res plasma is rounding its 5th year and shows no signs of giving up or being unable to cope with higher resolution/ quality pictures.
Try to avoid built in Freeview tuners if you can, they are not very good (for the UK anyway).