I have no real experience of printing Processing sketches with a printer...
But I can make some remarks:
- Jpeg: very good at compressing, but the more you compress, the more you alter the image. Should probably be avoided.
- TGA: not sure printers know how to handle this format... I see no advantage of using it, would be interested to know if there is any.
- PNG: great format, lossless, with decent compression rate (particularly with low color count).
- Tiff: A format printers like, it is (was?) used a lot in the PAO industry.
Notice that's not a single format, but rather a container. You can have, for example, various compression scheme, from Jpeg (with the artifact problem mentioned above) to Fax (for B&W) to several others.
- PDF: It is mostly a vector format (able to store bitmap information too), which is great for printing in some cases (if you make a drawing using a lot of shape functions), less in other cases (if you build your sketch pixel per pixel). Some generated PDF files can be too big, almost unmanageable.

There is no "best" format, as usual in the "what is the best" questions. It depends on a number of factors.
Lastly, the best way to know is... to ask to the printer you plan to deal with! (I supposed you want to output to large format, so you need to use the service of a professional printer.)