Which side of your brain do you trust most?

Ever since I finished writing a nonfiction book proposal a few weeks back, I have been contemplating the concept of the creative side of the brain competing with the literal side of the brain. The ol' right brain/left brain coming into play. Or perhaps warring factions.
I like to find a fountain pen and brainstorm, writing curlicue words interrupted by doodles on luscious pieces of paper. I like to write and play with words. I frequently like to edit those words. Admittedly, I'm not sure researching and discerning the market information for my book is my forte. Don't get me wrong, I love to research and expanding or following an idea. But it seems like the research portions of the proposal should be more objective, not the subjective like the creative portions seem to be.
What do I mean by subjective? Just like finding an agent, as the writer, you determine who you think your audience will be. But you have no real way of knowing who exactly will read your book, so you research other books that may be similar without the important ingredient of *you* and what you bring to the book. You are unique. How do you quantify that? How can you be objective about you? And, if you aren't being objective, does you literal side of the brain assert itself to the right side, insisting on being heard?
Fortunately, (I think!) I worked on the marketing research first, letting my right brain rest. Then I focused on the more creative aspects, sort of eating the vegetables before getting to the chocolate cake.
Does the creative side of my brain understand that? Will it appreciate that I consider it chocolate cake and perform for me when I ask? Or do I somehow need to start treating the left side better to rile up the right side of my brain, making it jealous?
What does your right--or left--brain think about all this?
Elizabeth King Humphrey is a creativity coach and the moderator/main blogger for CoastalCarolinaMoms. She has her own blog, TheWriteElizabeth, where she discovers creativity. Please note, no brain cells were harmed in the creation of this post.