Just to be clear, "Direct Lit" LCDs are, in fact "full array". You probably will never see one with local dimming however.
The reason direct-lit LCD exists is that it's even cheaper than edge lit. It uses super simple LED modules, pre-fabbed, in a similar design to older CCFL models.
The chassis can't be as thin as edge-lit however, so it's not for high-end product.
Oh, and that "even cheaper" is why edge lit has pretty much meteor-to-the-Yucataned traditional full-array sets.
People don't want to pay for it so it's pretty much extinct.
There is no difference in HDMI cables. If you can see the picture without visible dropouts or sparklies, the cable is working at 100%. No other cable will display a better version of that picture. You're simply wrong if you think there is a better digital cable than one that is already working.