Only the backlight is different. Both screens are LCD so the color and contrast producing mechanism is identical. You won't get better color quality or static contrast.
The 5 million to 1 contrast is dynamic so you will never see such difference on the screen at any given time. The LCD TN panel can only block out so much light to produce 1000:1 contrast and nothing more. Same with the samsung, it will only have 1000:1 contrast for practical purposes.
If you are paying something like $100 more for the LED backlit monitor I would pass on that. LED isn't that supurior by any means, it is only a backlight. Like the bulb of a projector it isn't really a game changer. If it is something like $20 then do it.
LED backlight is only good for a couple things.
No warmup time
Also makes the colors slightly colder and more blue so you get a whiter white but colors are affected so this isn't really a plus.
I'm not saying it is fantastic. We are talking about white here, so the picture will not be clearer, better etc. Just whiter.
To show what I mean. Take a pice of white a4 paper and hold it next to a "white" area on your screen. The paper is white. Your screen is not.
Of course, your eyes and brain gets used to your monitor, so in reality the difference wont seem as large at it may do if you put two screens next to eachother.