The Mac is more stable because very little runs on it, and so there is hardly anything to muck the system up, also because there are that few around it is not worth the hacker’s time, to bother with them.
With your old computer, you say you had a second drive that was an image of the first, which would indicate it was set up as a raid array, (Raid 1) which means if one of the hard disks failed you could swap it, and get all the information from the image disk.
However in Raid 1 mode, anything you do to one drive is automatically done the other, i.e. Load in a file and it is loaded on to both disks, Format the disk and both are formatted, and this will happen with any Raid 1 array, no matter what the system.
I would recommend a separate computer for your music system, so it can be optimised just for music.
Hope this helps

Bill