Not sure if it's still the case but for many years Apple's Core Audio was a big draw for people running audio software due to it's stability, performance and compatibility with various devices. I've used Windows with ASIO drivers for many years and always found it a bit buggy with occasional random drop-outs that can only be fixed by reinstalling the drivers. Pulse Audio on Linux can be even more of a nightmare to get working with your equipment, but I've heard it's improving recently.
That’s a good point. In my experience in studios (from around 5 years ago) windows is just about as prevalent as OS X at this point. I’m sure whatever niche you’re in does affect this however.
