Re: WHAT ??
It could be useful to compare [feature by feature] Gauche vs Guile. That would help to choose a right Scheme for the right project. Guile was here for awhile, why would we need another Scheme? Is there anything wrong with Guile?
I would recommend to compare first of all the following features: XML processing (including XPath and RDF), integration with web servers (CGI, Apache modules, standalone HTTPD), integration with GUI (like GNOME, QT or Win32), database API (PostgreSQL, MySQL), other communications (CORBA, SOAP).
Also, it would be useful to show the best and typical applications using Gaucho.
I think it would make more sense to explain the difference between PostgreSQL and other databases, like MySQL and Oracle, than between current PostgreSQL and its archaic versions.
Or give the short list of unique features at least: tell about ACID, MVCC, WAL, what makes it work as a high-end database server as well as a backend of web-application servers.