My personal favorite is TheManuz's. Although it was confusing when I first saw it, it seems to represent light and darkness well originally.
I actually thought for a second that, I might only consider this my favorite because I've seen it around in the last few days. Though I liked your design at first, being more clear to the first-time viewers that it is a mix between light and darkness even without explanation. However, it seems that it has been made rather quickly. Small edits (such as the border around 'dark' side that makes it look slightly larger) to make it look natural would be nice
On Kami's version, I thought that the colors were way to centered on 'darkness', to the point that I imagined a dark creature coming out of a hole..sorry