The first sig is the best, but could still use some work. The lighting is too strong, and you can see that by how dark Sharpedo is compared to the rest of the sig. Plus, you might have C4D-spammed this one. While maybe you only used two or three C4D's, but too much of it are visible, so it lowers the sig's quality.
For the second sig, those Bubble C4D's (are they?) aren't blended into the sig well, and just look really bad. They're isn't much lighting or depth either, making the sig look a little flat.