Say I compiled a .tex file into ps and pdf. Will there be a difference in printing speed between pdf and ps?
The short answer is PDF will print faster.
According to Adobe:
So why is PDF more advanced than PostScript? A PDF file is actually a PostScript file which has already been interpreted by a RIP and made into clearly defined objects. These objects are viewable on screen not in code, but in visual objects that everyone can see. Because these files are already interpreted by the RIP, they can be more reliable than an EPS or a .PS file when printed. Additionally, because EPS files and .PS files can be easily converted to PDF and viewed on screen, print service providers can benefit from seeing the file after interpretation but before they send it to their printing devices. This may allow them to see errors in a file before wasting paper, film, or plates. This can be a terrific timesaver for people who run service bureaus or operate printers, and the result is that files print faster, more accurately, and with fewer errors.
While the other answer is right, that the PDF-to-paper stage is faster (because the RIP stage is done already), if the original posting user is considering whether to generate a PDF and then print to the printer, or generating postscript which they then just dump to the printer raw, then the same amount of work will be done, in total. In fact, there may be some extra overhead with the creation of a much larger PDF file, which is them compressed, and which then includes more information (including fonts etc).
The difference is merely whether the RIP stage happens in printer or on PC. It is possible that, measuring from the time that the user clicks "print", if you were both generating the PDF, and then sending it to the printer, versus just outputting your document directly as postscript, that it might even be faster (in some configurations) to print postscript, if your PC/operating-system PDF library of choice is less performant on your system than the dedicated RIP in your printer.
In short, it is not always an optimization, to have your application (if this is what you wanted to do) generate a PDF then send that to the printer. If you don't need the PDF end product, and don't want to launch a preview (and save a tree) before comitting to paper, then skip the PDF generation, and you may not find any speed difference.
Of course, the smarter thing, rather than asking, would be to test your actual scenarios.
If your printer is able to consume PDF (accepts PDF as an input format for printing), then PDF printing is probably a bit faster. I say probably, because some PDFDirect printers do secretly convert incoming PDFs to PostScript first, fooling users to believe they contain a PDF RIP when that is untrue.
If your printer cannot consume PDF (even if it can consume PostScript), then you cannot tell in advance. It depends on your
- operating system,
- exact printer model,
- printer driver you use for printing,
- the currently used driver settings.
Depending on these factors, your OS' print subsystem and driver setup will convert the jobfiles (PDF/PostScript in your case) through a chain of converters/filters, and it is unpredictable how fast/slow that will work for each case. How do you open a PostScript file for printing? Or will you send it from the commandline to a non-PS printer? If so, how will it be converted to the real format your printer understands?
You should clarify your exact requirements and your environment, before you can expect any useful answer.
I'm pretty sure it depends on how your printer is set up: if you are going through ghostscript to a consumer-grade printer, it probably doesn't really make a difference; if you're printing directly to a smart printer which supports both, you'd best ask your printer manufacturer; if you are printing to a printer that can handle PostScript but not PDF, then the PDF will need some kind of translation -- this might be doable by with a PostScript program running on the printer, but whether that costs more than running application-generated PostScript code probably depends on what kind of code the application generates.
Personally, I tend to use PDF because this makes it so much easier to preview on (or print from) Windows machines, which are usually what I end up sitting at when I'm working on my LaTeX documents -- especially since I unplugged the monitor and keyboard from my Linux machine.
The only way to be sure which way is faster for your setup is to time the printing of a sufficiently-large document each way. (Does dvips time count? How about latex/pdflatex time?)