Mmm, eight entries so far, all lively and colourful in their own ways. I like. And I didn't even realise we're already two weeks in.
Short answer: I personally prefer the second. Both of your signatures are crowded, but the second one actually does that have that kind of impression.
At a first glance, the first signature looks like it's supposed to have the vibes of being solemn, as it looks like the guy is being engulfed by an abyss of blue. While the use of sci-fi-themed shapes (brushes, I assume) fits quite nicely, I can't help but think it's looking a bit too crowded around his neck and chest. Also, the object that looks like a blend of wireframes and C4D objects on the right side of the signature is great, but imho the considerably less-crowded gap between that object and Rin on the left doesn't fit in well.
The second signature is a nice, creative mess of intermingling colours. On some spots, however, they look a bit too messy, and I'm not sure how there's noise in some areas. For example, the semi-transparent horizontal line of red/yellow crossing through her head has some noise on it. The stains look like splashes of colours (is the noise intentional, and is that what you intended them to be?), though, so they're still fine. But the right side of the signature is pretty messy and full of noise. This sadly offsets the left side, which is great and the colours mix quite well.