Wow! So much incorrect information in this thread.
1. Airplay has been proven to be Bit Perfect with CD quality files (16/44.1). You aren't going to get a better signal than Bit Perfect. The actual playback device could be jittery, but that is typically handled by the DAC if you feed it a digital signal.
2. The Yamaha WCX-50 does have some several on board audio sources available, but it is limited when compared to Airplay and an iPhone. I have had my WXC-50 for quite a while and have played Hi Res, DSD, Airplay, Bluetooth, on board apps like Tidal, internet radio, SiriusXM. Airplay with similar bitrates sounds as good as any other source in my opinion.
3. AppleTV vs WXC-50 - The AppleTV does not put out Bit Perfect audio for your typical CD quality file. It upsamples to 48khz from 44.1. That being said, I doubt that most people would notice. However, most audiophiles don't like the idea of resampling their files.
If I wasn't going to use the video features of the AppleTV I think the WXC-50 does a lot more for audio (including support for DSD and Hi Res files). If you want video, obviously, the AppleTV is the better option.