SNORT is an open source network intrusion prevention and detection system utilizing a rule-driven language, which combines the benefits of signature, protocol and anomaly based inspection methods.
Farm Monitors scans every XenApp/Presentation server in the farm. When all elements are gathered, Farm Monitor pings these servers to see if they are online. You can also choose to monitor to see if specified services are running.
I feel the two editors are complementary, rather than antagonistic. They have a very different "look and feel", but that's not a reason for choosing one over the other. They were designed for different jobs, and I use both of them, depending on the job.