Hmm....very tough choice. Both of them are REALLY good and look like they required maximum effort. In fact, the second looks like it took even more effort to make than the first. That doesn't mean I like it better, though.

The second one looks way too busy and isn't colorful OR vibrant. It's a great piece of art, but I wouldn't choose it to be my wallpaper if I had to look at it in the desktop everytime I use the compy. The first one, though, looks very appealing to the eye and perfect for a wallpaper.

In other words, I'm voting for the First One!