LG is only using white subpixels, 8 million of them to be precise.
They are not, in fact, trying. Their manufacturing method will be an order of magnitude less complex than Samsung's; their power consumption wil be slightly higher. I doubt that most people will perceive much of a picture quality difference. There are reasons, in fact, why LG's picture make actually prove superior. At this current stage, however -- keeping in mind these prototypes have little in common with the final products -- I'd say the Samsung is a tad better. In the real world, that's just not going to matter. Especially not if LG's price is $2000 lower than Samsung next year.
Neither method has any advantages or disadvantages vis a vis blue lifetimes. Both displays use blue OLED material. If it ages faster, the color temperature will change dramatically over time. That said, I don't believe this is coming to market in a design that is going to cause problems in the first 20,000 hours -- which is roughly 8 years of "high normal" use.
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.