The version you should choose to update to would depend on the current firmware version. If you have a version prior to 1.9.6, I would recommend updating to 1.9.6 first before going any higher. When updating via the cable, you should be able to go from 1.9.6 or newer to any newer version.
You can subscribe to the thread found here for release notes (1.17 notes are not officially released by 2GIG yet, but it adds LTE compatibility and general Z-wave improvements).
Historical changes to previous versions can be found here.
Now, it does not look like this is related to a suretyDIY subscription. If you have a different current service provider I would highly recommend contacting them and asking if they will support the newest firmware versions.