In organizations with a lot of computers, using similar hardware wherever possible creates economies of scale. For support techs in particular, having standard machines makes it easier to provide consistent service, but we should not let loyalty to a specific platform blind us to other solutions when they are appropriate.
Equipment standardization is generally a good idea. Whenever possible, having as few "species" as possible to support makes life easier all around. Few of the organizations where I have worked have been able to replace hardware in such volume that we could standardize on a specific model at any time. We have held to soft standards, though, usually buying similar model revisions from a single specific vendor each purchasing cycle.
Our standard desktop machines have Windows installed. Not because I have any problem servicing Apple hardware, but because Windows is the most cost-effective choice for our work. In addition to receiving competitive prices from our hardware vendor, our university offers certain volume-licensed software packages for Windows at significantly reduced prices. Comparable deals on Macintosh-compatible software do not exist.
Not long ago, our division outsourced the graphic design of our published research reports. Our in-house designer had left the organization, and we hired a new manager who would be coordinating the production of our publications. This new employee was not supposed to be doing any layout or graphics work herself, and coordinating with our design contractor was only going to be one part of her job portfolio. When preparing for the publication manager's start date, I saw no reason not to provide her with one of our standard Windows desktops.
The only problem was that the designer the management team had chosen used a Macintosh-based workflow. Complications arose for our publication manager almost immediately because we had her using a Windows machine. Even though all the design programs exist for both platforms, when your printer and your designer are using Macs, life can become difficult if you insist on using Windows. The biggest issue for us was fonts. Our publication manager would want to make a small edit to the text in a PDF using Acrobat, and we would discover that the Windows version of a specific font would have slightly different character spacing than the Macintosh version. Any edits made on our end would throw off the text flow in the document.
When we tried migrating our publication manager to a Mac, her problems went away. The other tasks she was responsible for did not necessitate any specific software that required Windows, and by using a Mac, she found she fit in better with the design and print process. By making an exception to our usual standard, we were able to provide her with a tool that better suited her work.
Standardization can certainly make working the help desk easier, but techs should always bear in mind that IT is about providing the right tool for the job. Sometimes, that might mean making an exception to the usual standard.