It depends on what you have and what you expect out of it. This is a case-by-case answer that we are happy to discuss with you. Most PCs are good for about 5 years (give or take) so we can walk you through the decision process with a little info on what you have now and what you do with it.
If you always used Windows before, you will be learning something brand new with a Mac. They are great systems, but different, and about twice the price. If you are in an office environment that is mostly Windows, you may want to stick with Windows just to avoid the compatibility issues with files, printers and sharing, unless you are more advanced in computers. It all works, but sometimes it takes a special driver for the Mac to print to the network printer – that sort of thing.
For offices we recommend either black only laser printer (or multi-function devices). If you need color we recommend a color laser printer which are now fairly affordable. Leave the inkjet models for home use and if you do get an inkjet, be sure to not buy the cheap models ($100ish) as the cost of replacing the ink will break you!