An introduction to computer audio
Discussing differences in sound quality between Mac and Win on an audio forum is almost impossible. Most of the time it ends up in a flare.
A reasonably sane one can be found here.
If what you want to do can be done in the MAC then you will have the easiest time doing it this way, but probably not the cheapest.
If you want the flexibility to do the most things, especially run the widest choice of software, you will be better served with a Windows machine. Unfortunately this flexibility comes at a cost: increased opportunity for obscure problems, increased risk from malware and increased need for maintenance.
In the end you are probably better off sticking with the devil you know unless your situation has become untenable.
Windows offers a far wider choice in software.
Players like JRiver Media Center, Foobar, etc.
Rippers like EAC or dBpoweramp
Taggers like MP3Tag
You have more options to configure the system to your needs.
The MACs have become popular in the audiophile community, there are sufficient alternatives for iTunes.
Win integrates well with other products.
Moving your audio collection from Win to a music server or a DLNA compliant NAS is a pretty straightforward process.
If you want to export your audio from iTunes on OSX to another music server you really have a job to do.
See Guide To Converting From iTunes To Dedicated Music Server for an example.
You can choose almost any piece of hardware because that's where Windows is about, supporting each and everybody's hardware.
You can choose from a wide range of sound cards.
However when using a laptop or an outboard DAC this argument is not relevant.
OSX supports UAC2 (USB Audio Class 2) natively.
You need a third party driver for Win if you want to play sample rate > 96 kHz on Win.
The downside of this flexibility is that the system becomes more complex.
Third party software and hardware might come with third party bugs.
Apple’s absolute control in principle improves stability.
I do think the interfaces most of all have more in common that that they differ.
Both keep it simple, an interface allowing you to do the basic things.
Both have a secure mode; both are equally badly documented about how this works.
Both don’t support AccurateRip.
Both use an online database for tagging. In case of iTunes you have to open an iTunes account and hand over your credit card number first to get cover art.
Cover art is where iTunes shines. WMP reduces it to 250x250
Both have their proprietary lossless format, ALAC ( Apple Lossless) and WMAL ( Windows Media Audio Lossless).
The Apple Lossless Encoder (and decoder) was released as open source software under the Apache License in 2011.
Both don’t support FLAC natively.
Both can be configured to play FLAC using third party plug-ins.
Both iTunes and WMP players won’t allow you to bypass the audio engine of the OS.
In case of Win you can bypass the audio engine using drivers like WASAPI or ASIO.
You need a media player like JRiver or Foobar allowing you to choose an audio driver.
In case of OSX there is a HOG mode, giving you exclusive access to the audio device.
Some media players can bypass the OSX mixer (integer playback) giving you a straight unaltered audio path.
Out of the box both will resample everything to the rate set in the control panel.
According to dCS, OSX does a better job than Vista but they don’t consider it being ‘audiophile’ grade.
However, you can set the sample rate to match the sample rate of the recording manually to avoid resampling.
Microsoft is a DLNA member, Apple isn't.
DLNA is the industry standard for streaming AV.
Win has good DLNA support, OSX not.
If you want to integrate all your AV gear regardless of its brand, Win is the platform of choice.
iTunes is an interface to the audio collection.
QuickTime does the actual playback.
The QuickTime output goes to the Win audio engine.
Now you have 2 audio settings, the one in the QuickTime control panel and the one in the Win audio control panel.
If you play Redbook audio (16 bits/ 44.1 kHz) QuickTime might upsample this to 24/96.
If you have set Win to 16/44 the result will be downsampled to 16/44
Two times sample rate conversion are two to many.
Set QuickTime en Win to the same values to avoid this.
From iTunes 10.5 on, QuickTime is no longer needed on Win.
As you might have expected, claims that OSX sounds superior compared with Win and visa versa are often made on audio forums.
This is about perceived difference, very few bother to measure anything.
Mitchco  compared the output of JRiver on Mac and on Win.
Mitcho’s test is a digital loopback recording.
This tells you everything about the bits.
Yes they are the same on Mac and Win.
As expected, a test at bit level doesn’t make a difference as long as both platforms are configured to deliver bit perfect output.
That is inherent to the digital domain, the bits remains the same unless altered somewhere.
By design a bit test says nothing about the other half of digital audio; the timing.
Archimago , using various PCs and Macs, recorded the analog out.
This tells you much about the jitter performance of the hardware used.
The onboard audio of the Macs are better than both the Asus and the Aspire.
Using an asynchronous USB interface, the Macs produced slightly more sidebands in the J-test.
When combining the asynchronous USB with Toslink, providing galvanic isolation, the differences disappear.
Obvious the protocol used (asynchronous USB) and galvanic isolation are far more important than the platforms used.
There is no evidence Mac or Win behave different sound quality wise.