There is a lot of functionality to consider whenchoosing the correct edition, below are some key features:
Go edition
Internal database limited to 200 records
Limited to 5 card templates
Premium edition
Can connect to csv, Excel, Access and SQLite databases
No limit on the number of records
No limit on card templates
User based logins
Professional edition
Can connect to MySQL, SQL Server and Oracle databases
Automated face-Cropping built in
Group based logins
Conditional layout support
Business edition
Support for Mifare Classic encoding
Support for reading HID Prox cards and iClass UID numbers
Enterprise edition
Support for Mifare Desfire encoding
Connect to LDAP to read/update records
A full list of features for each edition can be found here.