I have a relatively small table of data I would like to insert into my thesis. Is it better to natively create a table, or to externally create the figure and insert it?
A table of LaTeX code is only a chunk of text that could be placed inside the main document or in an external file, at convenience, but as an image could be only a heavier file (JPG, PNG), placed externally, may be of medium (PNG), low (JPG) or good quality (PDF) but anyway you cannot edit the table directly, so should maintain also the source-s file to create that table (spreadsheets, etc.). Let'see: At least 3 files instead of only one for a small document with a single table. If the document have, said, 20 tables, the source files might be up to 41 editable/non editable files (surely many Mb) instead of a single file of ridiculous size.
Another issue is the quality of the table itself. Using images will be difficult match consistently the font sizes, font styles, interline spacing, spaces above/below the table, etc., with the rest of the document.
Finally, make tables in LaTeX need some learning, but then make/edit elegant tables is easy. When you know enough, edit a table in a WYSIWYG word processor is pain. If that is not enough, you can import data from external sources in several ways (as cited by Bernard,
datatool, but also exist
odsfile ...) not to mention R/knitr for the automatic generation of LaTeX tables.
These aspects are not a matter of opinion, but it is how important are for everyone and the weight of the circumstances. It could be understood use a screenshot of a table taken from a web page, for instance, in case of emergency (experts), ignorance (novices) or impatience (bunglers), but for me (me and my circumstances) there are no doubt: never ever.