While the purpose of Scott Motte’s presentation might not have been to compare MongoDB vs CouchDB (see the slides embedded below), the blog post linked from the title has a dedicated section on it that comes out as a half-baked attempt to (partially) compare the two, pretty much lacking the technical arguments, but having quite a few quotable bits:
map/reduce is difficult to grasp and couchdb’s map/reduce feels like a neutered version
Use mongodb for your traditional web app - where your users are doing a lot of updates but where you are generally controlling the interface and features.
Use couchdb for focused web apps that are mostly an api or web hook and where your users are controlling the interface.
[MongoDB] ’/50s kid (Traditional, yet rock n’ roll, fast cars. Feels comfortable yet feels like the future. good for traditional web apps)
[CouchDB] indy kid (Untraditional, crazy cool ideas (like embedded apps and running in your browser), but uncertain. better for untraditional web apps right now)
The slide I have found interesting (and included it below) is the one listing MongoDB mappers. That would be a nice addition to the NoSQL Libraries page