We have used a few products like NWEA/Map, Lexia Rapid, Curriculum Associates/ i-Ready Diagnostics. Renaissance/Star360 stacks up to all of them, but doesn't exceed them. Star360 has less basic features (like school level grouping, exporting reports as a csv file, saving previous student data) but has some very good specific features compared to the others (like quick testing time, a variety of quick, good classroom level reports for teachers). They all have pluses and minuses, so it depends on the issue/feature is most important to you.
NWEA/Map: the plus is complete previous data accessibility and export and compatibility in that most district in the county as well as our ISD use it., minus is the length of time it takes to test.
Lexia Rapid: the plus is it gives very detailed breakdown of information in a relatively short test; the minus is it is VERY limited in scope (Reading at the k-2 level).
Curriculum Associates/iReady Diagnostic: the plus is it has an integrated, ongoing online instruction piece that is tailored based on the diagnostic assessment results; the minus is that it does not give any good summary data (it gives individual scores and levels, but no class or grade average scores etc.) and it does not statistically adjust the normed scores (percentiles) for weeks of instruction or date test is taken in relation to the norm study.
Renaissance/ Star360: the plus is that is it a quick assessment leaving more time for student instruction, it has a variety of good, detailed classroom level reports, and it interpolates the results to account for the exact testing date in relation to their norming study; the minus is that it does not keep records of previous students (even for the remainder of the current school year), it does not allow reports to be exported in any manipulable form (only pdf), and its lack of well functioning school wide grouping.