Choosing the right printer is hard enough when you have all the information you need. It gets harder when manufacturers tout printer specifications that don't tell you what you need to know. Here are some specs to be wary of and others you should ask about, even though manufacturers tend to skip them.
PPM (pages per minute) speed claims for lasers are close to the actual speed for printing simple text files at reasonably high quality. But for more complex images, such as intricate graphics, a slow printer engine with a fast processor can beat a fast printer engine with a slow processor.
Ink Jet Speeds
If you take the claimed speeds for ink jets seriously, you'd have to conclude that most ink jets are as fast as or faster than most desktop lasers. They aren't. Claimed speeds for ink jets are based on draft modes you wouldn't want to use very often, and even for those draft modes, the claimed speeds are faster than you'll see in real-world use.
Duplexing Speed: A Missing Spec
Most manufacturers conveniently leave out a rated speed for duplexing, because most printers can't print images on both sides of the page without slowing down significantly. If you print in duplex a lot, it's worth finding out the speed for duplexing as well.