Managing both Windows and Mac environments, I've never had Apple software "break" hardware. Never had to find an updated driver for the legacy pin-printer for the self-carboning invoices, due to an OS upgrade, service pack or security update.
I tell my Windows users - ignore all prompts until I can be in the building. I tell all my Mac users - let it run, the updates will be fine. That lowers my employers TCO, as I'm not going to spend $X time X computers fixing things that used-to work.
As to hardware choices, Mac's were at one time built like battleships. Could you just go and clip-in the latest AMD or Intel processor, overclock that bitch and... oh, wait - that's Gamerville and not Corporate America.
No, instead a robust back-end usually accomplished on a Mac, tasks that choked a similar-era low-end PC. A commercial-duty PC built-up, would be a different thing, and cost the same as a then-current Mac. Example: Dell 470 Workstation with dual Xeons, 8 GB of RAM, and dual SCSI drives would keep up with a similarly built mac, AND cost the same when new. Oh, but remember, you have to have the higher-end MS operating system and increased $ or that 8 gigs of RAM won't be recognized. Oh, and your PC software may have to be patched as out-of-the-box, it may not attempt to access that RAM.