Hi, Glenn

JRS 5.0 can be used with RTC5.0. Since this is the entry version of JRS, you may find some custom attributes not yet supported in JRS and less features in JRS5.0 comparing to latest version 6.0.2(you can find the new features in
v6.0.x JRS here: https://jazz.net/downloads//jazz-reporting-service/releases/6.0.2?p=news).
Comparing to RRDI, you may find it is easier to configure and use JRS but JRS may still have less features than RRDI at this moment(RRDI can create crosstab type of reports but JRS can not for example). But JRS has  advanced feature by using SQL directly to achieve some features not yet support through UI.

Going forward, RRDI is no longer supported from v6.0.x and you need to migrate the reports to Cognos BI if you want to continue using RRDI reports. In the future version, even this migration path is no longer planned. Therefore, it is obvious JRS is a focus for CLM products and more and more features are implemented into JRS version by version, it is highly recommended to start using JRS now to get familiar with it.

Hopefully this helps to some degrees.