Choosing the format in which to output a specific file depends on how the file is to be used. For example, JPEG is good for photographs and TXT for text, but if you need to output a medical file (which may contain images and text) then only DICOM will do.
The following table matches function to format:

Task

Suitable Formats

Exporting to images

AFP

BMP, PNG

DCX/PCX

IMG, IMG Barr format

JPEG

PDF, PDF/A

TIFF

Exporting medical file

DICOM

Exporting to Page Designer 'pen and paper' iconPage Designer

FDL

Exporting the document

EMF

HTML, HTML5, MIME-encoded HTML

IDF

IPDS*

PCL

PDF, PDF/A

PS level2, PS level3

RTF

XPS

Exporting data fields

CSV, TXT, XML

IDF, RTF

Extracting text

IDF, RTF, TXT

Extracting part of original document

IDF

Macro

RTF

Subset

Archiving

DICOM

PDF, PDF/A

TIFF

TXT

XPS

Printing (MS Windows)

Print

Production printing

AFP

PCL

PS level2, PS level3

IPDS*

IMG

Web publishing

HTML, HTML5, MIME-encoded HTML

PDF, PDF/A

PNG

*if you have the IPDS option installed