My experience is that those all-in-one devices are trouble. Drivers are not always available, or are huge. Then, one bit goes on the blink and you have to replace the lot.
I bought a decent scanner (not expensive) and separate printer. The two do take slightly more deskspace.
I'd recommend separates, and reading the reviews on Mac and PC websites to see how they perform. There are so many new models released every month that what was the ideal product when I bought mine is probably now obsolete.