Hmm, lemme see. I'm still learning about reviews and such so, I'll try this. x..x
1st banner -- Okay, well, there's not much of a focal point here, now is there? =o And depth ... I don't see much depth put into this banner. And flow ... I'm not sure, but did you make is so that the c4d would be the flow? o..O The tex is okay, but there could be improvements. Maybe, drop shadow effect would be a nice effect for the text? And, I'm not really sure if there's any lightsource. To me, this is banner is a little plain. The thing I like about it, is the theme colors you used.
2nd banner -- Ah, okay, there's a light source here. ^..^ Err, I'm pretty confused with the flow. The render, kinda sticks out weird. Have you tried, maybe, smudging with the render? =o I think it could be a good idea. The text here, well, try another font and text style. Try adding outlines to your text, or the drop shadow effect. The theme color is okay, but eh, still plain to me. And, again, I don't see much of a focal point, since there's mot much depth to it. I think depth makes it easier for people to see the focal point in a banner. Again, that's all I have.
Yeah, maybe I'll come here again to review someone else's banner. >..o;