Up-to-date version comparison and feature list can be found from here.
As for time being there are three versions of Sirid available: Lite, Standard and Professional. The first is designed for individuals or small teams, the second for small or medium-sized teams or companies and the third for medium-sized or large companies. All versions have the same basic features but Standard and Professional versions have many advanced features. Both Lite and Standard version have restricted user amount. For more detailed and up-to-date information click the link above.