Assuming that either 65" or 70" is ok by you just in terms of screen size, the question of whether to get a very good plasma or a good LCD comes down to your viewing environment, IMO.
In sheer measureable metrics - like black level, off-axis viewing, color uniformity and REAL contrast (not the made up "dynamic" contrast numbers that all manufacturers quote), the best plasmas still outperform LCDs. But there's one, key issue, which is that plasmas don't look their best when the room is lit!
In a dim or dark room, a top level plasma is the best choice.
But in anything more than "dim" lighting (as in
just barely enough to read a newspaper level of light), plasmas start to wash out a little bit, and those lovely, inky blacks start to turn grey
Up until the 70" Sharp LCDs came out, there honestly wasn't a single LCD (LED backlit or otherwise) that I would have recommended! The reason? ALL current LCDs use a ridiculously glossy screen surface that makes them utterly unwatchable in anything other than pitch blackness! At least to me
But thank the heavens, Sharp smartened up and made some matte screen LCDs again! Hooray!!!
The LC-70LE7xxU series are the ONLY current LCD TVs that I recommend! And thankfully, they're really good! They use a full-array LED backlight for even illumination of the screen - none of the crappy "edge-lit" LED nonsense or the "cloudy" CCFL backlights. The backlighting is NOT local-dimming, but the 700 series Sharp models still produce nice, deep black levels. They are very bright. The color reproduction is good. And Sharp gives adequate user controls to dial in the color and greyscale performance rather well. For similar controls in a plasma, you need a Samsung or the VT30 series Panasonics. The GT30 series lacks everything but the most basic user picture controls.
So, very simple - if you have lighting that is any brighter than "dim", I'd recommend the LC-70LE734U if you don't care at all about 3D or the LC-70LE735U if you DO want 3D. Same television, just 3D vs. 2D-only