Comparison research monitoring software - Nagios Zabbix Muni

For monitoring some websites on an Ubuntu (version 10.04) server, I want to install monitoring software. For this I would like to receive a comparison report between these 4 monitoring software products: Nagios Zabbix Munin Cacti For each of these 4 software products I need a detailed explanation howto install the monitoring software, including screendumps of every step in the installation, howto setup user accounts etc Also in the documentation I would like to read detailed steps howto configure the monitoring of the following devices: CPU utilization, memory usage, diskspace, network interface data I/O Finally after all, I would like to read your opinion, of which of these monitoring products you would like to use and your motivation for that specific product.