Sales are better, because they make Amazon's algorithms add your title to other book's Also Bought lists. People who look at Sunbolt or The Thief Who Pulled on Trouble's Braids now have a chance of seeing your book, because I bought both of those books within the past couple of weeks. The .99 may not mean much, but the chance of discovery is... well, as far as I'm concerned, Amazon's algorithms are far more key to success than any number of reviews. Reviews are nice but Amazon's algorithms are how books get found in the first place. And I'm happy to donate .99 to support another indie.
Edited because I forgot reddit doesn't use normal HTML...