A surprisingly balanced comparison between Mongo and Couch is posted on the Mongo docs website. While the focus of technical talking points drifts towards Mongo, this is inevitable, as the doc is written from the perspective of Mongo experts. However, the writing is not pre-disposed to favor Mongo as a one size fits all solution, and the author goes out of his way to point out that Couch is more suitable for some situations (such as master-master database solutions where this is a high degree of geographical, often offline distribution). Read the entire doc here.