I knew I liked Jake Clark's design for my book cover the moment I saw it. He had a different take on my design brief than the other designers and there were some layers of meaning that could be interpreted in what he created.
But as the saying goes, I'm not my audience. So I used a poll with Jake's design along with several other VERY good designs that I thought worked well with the book I'd written. Admittedly, it was a tight race, but my audience agreed with me. Jake's design was a winner. More than one person who took the poll told me that they'd pick up the book based on the cover he designed without me telling them what my preference was.
He was also REALLY easy to work with in refining the cover. I highly recommend him.