Preview has a documented PDF-reduction workflow through File > Export, including a Reduce File Size filter. Apple warns that quality and output size vary. Apple Support: Reduce the size of a PDF in Preview on Mac
FileStation offers a browser workflow and describes distinct compression modes. That may suit someone who wants the same web interface across devices, but the actual result still needs testing on the chosen browser. [P01, P03]
Choose Preview when its existing Mac workflow meets the task. Consider FileStation when a browser-based document workspace is more convenient. Do not assume that web-based means server-uploaded, or that desktop-based means automatically suitable for every confidential document.
No head-to-head performance test was performed for this comparison. It compares documented workflows, not speed, quality or security superiority. Link to both vendors’ documentation and show the review date.