Where is a user guide for Alfresco

I bought CMS Watch's ECM Report, it contains a very detailed comparison. It is not free though :-(

And all other comparisons I could find are already quite old... sorry :-/

Try asking on Nuxeo and Alfresco's forums.

We have implemented the same thing for one of our client, Earlier we had the same approach but found difficult to integrate the Varnish cache with liferay , So we added the Caching framework at Service layer and cache the alfresco content, And accessed the content VIA Java web api.