What is a UFR II printer driver and why might I use it in preference to another type?

UFR II is the 2nd version of UFR... which stands for "Ultra Fast Renderer". In short... it's similar to PCL in concept... but alien in the actual instructions. Most commonly associated with Canon printers. PCL is more generic, common, and simple, but antiquated... UFR II is better designed, and faster, but not anywhere near as common. If you have a printer and driver that both are geared towards UFR II... use it. If not... PCL is a lot more forgiving.

UFR is a proprietary, non-standard rendering engine that is functionally similar to Postscript and PCL. UFR is risky given that Canon can make it obsolete at any time based on their whims.

In general, I shy away from printers that don't properly support open standards such as PostScript. Both PostScript and PCL are very fast and very well supported by the industry. In fact, PDF documents are more or less based on PostScript.

UFR? You have to ask Canon nicely if they want to help you out.