As the provided Version Comparison Chart is really incomplete I've created a list of (hopefully) all features which are disabled in the Essential Firewall:
- automatic firmeware updates
- automatic configuration backups
- user portal (would not make sense)
- High Availability (HA)
- external authentication servers (LDAP, AD, Radius, ...)
- Time Events
- Network Link Aggregation
- Network Uplink Balancing
- Network Multipath Rules
- Network Policy Routing
- Network Dynamic Routing (OSPF)
- Network Quality of Service (QoS) Traffic Selectors
- Network Quality of Service (QoS) Bandwidth Pools
- Network Multicast Routing (PIM-SM)
- DNS: Request Routing
- Network Intrusion Prevention (IPS)
- Network Server Load Balancing
- Network Generic Proxy
- Network SOCKS Proxy
- Network IDENT Reverse Proxy
- Web Security (including all HTTP/HTTPS and FTP proxy services)
- Mail Security (including all SMTP and POP3 proxy services)
- Mail encryption
- VoIP Security
- IM/P2P support
- Site-to-site VPN
- Remote Access SSL VPN
- Remote Access IPSec
- Remote Access Cisco VPN Client
- Logging: Remote Syslog Server
- Logging: Remote Log File Archives
- Reporting: Exceptions (useless without web or mail security)
- Reporting: Anonymizing (useless without web or mail security)
- Reporting: Network Security -> Packet Filter
- Reporting: Executive Reports archiving and automated creation
If you find anything else, feel free to extend the list ;-)