I needed a powerfull to provide me with information that Google Analytics doesn’t bring such as bandwith consumption, IP addresses etc.
By the way, I used this very well-made tutorial to setup awstats: http://koo.fi/blog/2012/12/01/awstats-multi-site-setup/
And I also that one to use awstats with Nginx http://blog.horsducommun.be/2012/12/26/nginx-and-awstats/