Unfortunately, the locally-lit LED tv's have all but disappeared - if I could find one, I would buy one. Sadly, this TV is not one of them. It does feature smart dimming, but alas it is indeed edge-lit. This means the LEDs that illuminate the screen are arranged on the sides of the tv instead of directly behind. The smart dimming feature does help if there is a clear line between the light and dark parts of the scene (ie top & bottom) but it is nowhere near as effective as a locally-lit tv.
CALL VISIO ALL IT NEANS IS THAT ITS THIN IN DEPTH
I think your asking about the the difference between this tv and teh E551I-A2....both are e series. this tv is direct led while the latter is edge lit led or in vizio speak razor led.
If you want the best picture quality get this tv because it has smart dimming, which i wont waste time explaining but most people confuse with ambient light dimming ehich is more annoying than helpful...just know smart dimming makes a big difference.
On the other hand if you like technology that has more problems and cant stand to have a 4 inch thick tv as opposed to a 2 inch thick tv feel free to spend the extra $30 - $80 on the E551I-A2