Your seating distance and your ambient light level determine which TV you ought to buy.
8-10 feet is a fairly wide margin when it comes to figuring out your ideal screen size. At exactly 8 feet away, the SMPTE recommended 30 degree field of view would equal a 60" diagonal screen. At 10 feet, the same SMPTE recommendation would equal a 74" screen. So figure out your exact viewing distance if you really want to nail the perfect screen size. But the general 65" to 70" screen sizes should be just about right for your seating distance range.
In terms of pure measureable metrics, the Panasonic VT30 plasmas are the best flat panel displays available at the moment. The VT50 models are due later in 2012. Panasonic's top-level plasmas offer the best black levels, perfect off-axis viewing, excellent color accuracy and uniformity, plenty of user adjustment controls to dial in black level, white level, grey scale and gamma, and the ANSI contrast and general film-like quality of the image are about as good as consumer displays get.
The one downfall of these plasmas is that they only look their absolute best in a dim or dark environment. Due to the glass screen surface, they still wash out a little bit with normal or bright lighting, leaving those lovely, inky blacks looking grey and dull. Reflections and screen glare are not bad at all due to the screen coatings. But simply put, if you want the best image available and you have a dim or dark viewing environment, then a Panasonic VT30 65" plasma is your best choice.
The only decent alternative on the market are the 70" Sharp LED-backlit LCDs. And NOT the Sharp Elite LCDs. People think they look great - and they do - in a COMPLETELY pitch black room. However, the Elite models have a mirror-like glossy screen surface that I find completely unwatchable when there is any amount of light in the room. I do not, for the life of me, understand why almost all LCD televisions have these stupid super-glossy screens. But I find that they make these televisions completely unwatchable. I cannot stand seeing my own reflection looking back at me no matter what is being shown on screen. It's a travesty!
The only large screen size LCDs with matte screens are the current 70" Sharp models. If you do not care about 3D, you will want the LC-70LE734U. If you want 3D as an option, you'll want the LC-70LE735U.
Sadly, Sharp is discontinuing these models as the new 74x series arrives. The reason I say "sadly" is because the new 2012 replacement models now use crappy edge-LED lighting, giving them all the problems of uneven illumination that come with stupid, crappy edge-LED backlights.
The 734U and 735U use full-array LED backlights with NO local-dimming. This is the best backlighting option for LCDs IMO. Local-dimming creates "blooming", which shows up as "halos" of light around small bright objects on a dark background. The Elite models use local-dimming and they have blooming. Yet another reason to avoid them. Although the glossy screen already renders them utterly useless anyway.
The new 94x models will be the new "flagship" Sharp LCDs, but they too use local-dimming. So now is the time to strike! If you have normal room lighting or bright lighting or sunlight, get yourself a Sharp LC-70LE734U or 735U before they are all gone! They are a rare breed of LCD that looks as though will only exist in this one model year. They have everything you could want from an LCD. An even backlight with a full-array LED source. A matte screen so that they can be used in normal to bright lighting where plasmas wash out and look grey. Very accurate color with plenty of user level adjustments. Very bright output if you want it - perfect for a bright room. The absolute black levels are not as black as the VT30 plasma, nor the local-dimming LED backlit LCDs, but that is where the decision becomes easy:
dim to dark room - get the 65" VT30 or VT50 Panasonic plasma
normal to bright room - get the LC-70LE734U or 735U Sharp LCD.
These are really the only displays worth considering in your situation, so it's really rather easy
