All advertised contrast ratios >1500:1 (yes, 1500) are dynamic contrast ratios, and therefore mostly useless. The one that matters is the static contrast ratio, which is usually around 1000:1 or so for modern LCDs. Unfortunately, dynamic is the one usually advertised, since it makes the product look better in the specs.
3. Wider color gamut; I think using the "right" LEDs the gamut can go 140% color gamut. This is not really a benefit for those who want color accuracy on screen in a program or OS that is not color aware. This is a major sticking point for graphic artists.
4. "Dynamic Contrast Ratio" is the buzz phrase, they wow you with huge numbers. Just be aware that difference between the lowest and highest contrast ratio displayed on the screen at the same time is equal to the static contrast ratio. Example: 1,000,000 to 1,001,500 or 1,450,000 to 1,451,500.
LED backlighting in PCs and HDTVs operate slightly differently. In PCs all LEDs are either always on or always off. LED backlighting in HDTV are different for some of the higher end HDTVs. They use LED backlighting with local dimming; sections of the screen can be dimmed or turned off while other sections of the screen remains bright.
Examples of HDTVs with local dimming LED backlights:
1. Samsung A950 series (last year's flagship model)
2. Sony XBR8 series
3. LG LH90 series (I have the 47" version)