What's the difference between these two RAM boards?

[RisingSun]

G.Skill 4GBNT and G.Skill 4GBNS. One costs $24.99 and the other is $22.99. The cheaper is rated better.

 

[M1kkelZR]

There is no real difference.

 

[johnb35]

Looks to be just the black circuit board compared to the green board.