It's all down to how FileLocator Pro pre-processes documents for searching. If you have 'Enhanced File Searching->Office/PDF documents' checked in the Options tab then FileLocator Pro will pre-process any file extensions shown in the Settings link:
The pre-processing involves converting the file type to text for more accurate searching and presentation but can slow down the search. If 'Deep Search' or 'Also search raw document data of processed files' is checked then a file might be searched twice, once using the pre-processed data and once using the raw-data.
Agent Ransack, by comparison only pre-processes a fixed number of file formats (pdf, doc, xls, ppt, docx, xlsx, pptx, odt, ods, sxw, sxc) and doesn't allow 'Deep Searching' of files.
- ZIP, 7z or other compressed format searching is switched on in FileLocator Pro.
- Outlook PST or MSG searching is switched on in FileLocator Pro.
Agent Ransack can't search either of these types of formats properly.