@Bart-Slegers - we moved from Crystal to JSReport almost 3 years ago. Obviously, these are two completely different architectures; so comparisons aren't really valid. The number of records is almost irrelevant. For our reports they take approximately 5 pages per seconds. One other reason for performance degradation was dynamic headers or footers (for example, if the footer says page x of y). We found some settings that speed footers up.
But if we estimate that the number of pages is going to be very large, then we split the job and submit to JSReport in parallel, and then merge the parts using PDFSharp.
Overall, we found that using some analysis, and asking questions on this forum, we were able to achieve acceptable performance even in very complex reports.
Note: We are only JSReport customer; @jan_blaha doesn't pay me for saying good things about his software; although I don't mind ;)