What's the difference between these drivers?
PCL6 (or Printer Command Language, Level 6),
PS (or PostScript) and
PPD (or PostScript Printer Description) are all ways a printer can "communicate" with your PC via it's driver and define how the page will be "drawn" by the printer (text or otherwise).
Which one should I use for my installation? Should I just check all of them?
You'll have to refer to the manual for the specific printer you are installing to see which driver to specifically use when printing; although installing all of them won't hurt anything, you'll just need to be sure to choose the correct driver when using the printer.
XPS or the XML Paper Specification is an 'open' driver standard made famous via
Microsoft's XPS print driver. It's another way to communicate to the printer (if the printer understands XPS).
If you install the Microsoft XPS viewer (and subsequent XPS drivers), it will give you a "virtual printer" that you can then print to a file (as it would be printed on paper). You can view the
.xps files with an XPS viewer and physically print them later. Anecdotally, I use XPS on my Windows machines when I might want a printout of some important information that I can physically print later (without having to waste paper or if my network printer is offline at the moment).
It should also be noted that vendors often times have one suite of software for an entire line of hardware with different capabilities; this is why you'll see driver packages like this that will have a slew of options even if your specific device only supports one or two of them.
In the end, you should be able to select "all" and Windows and the printer can determine which driver would be the best to use (or at a minimum you can uninstall the incorrect driver).
Hope that helps.