Both have advantages. TIFF is a native image format that allows you to use built-in annotations and features such as merging pages without buying Adobe software.

PDFs are optimized for long term storage since the data is metadata instead of pixel data. Only when you view a PDF does it decode to an image in memory, the data is stored in a simpler format than pixel data if the PDF was created from a digital system.

In other words if a PDF was not created from a picture, it is not a picture on disk, only in memory when opened. A TIFF is always a picture and a picture requires a lot of disk storage space.

One other less known advantage for exported TIFFs is that redcations are direct modifications to the pixel data (once exported from LF) and the information behind them is gone. A redacted PDF (that is not an image) is metadata and the data behind the redaction still exists in the file which can be found.