Exporting Activities: Bulk API vs regular

Hello,

just wondering if anybody else is using both Bulk and regular API to export Marketo activities for offline analysis. Given the same filters (activity date and type), comparing 2 results, BULK API appears to return a subset (roughly 70%) of what is returned by regular API - some activities are missing. The same outcome does not appear to be limited to just a particular activity type or date range. Anybody else came across a similar situation?

Thanks,

Ged