First sig. This is the lesser of the two, imo. Number one, not enough contrast. You have loaded this sig with light colors, but are missing the darks to bring out the lights, and make it easier on the eyes.
Ok, for lighting, i notice that there is a light source top left, and it is producing light as a litghsource should, but does this light not cast shadow? Try to make the right side of the sig darker because the light on the left. Just laws of lighting.
The text on this one should be... more... colored I guess. I would move it a bit to the right, and up a little, and add a hint of yellow into it, just for beauty's sake. more color in the sig, and the face is already too white.
Second. I really like the whole lot of this sig, but i will point out a few things.
Some parts of the c4d render, or brushing, or w/e it happens to be, seems to overlay, like top middle area. It looks a little like the thing was clone stamped, something that you don't really aim for. The text placement here is pretty good, along with the color, but I really don't feel this text that you have chosen here. It is taking up a lot of space, and it is grabbing the attention from your beautiful c4d things.
Overall, this sig is pretty good, and I love the coloringon it.
