Just you. The music data is not passed through either i-phone or i-pad or anything else running the Mosaic control app.
It is amazing how we human creatures have our senses affected by all sorts of unconnected factors. Perhaps you found the sound cleaner because the image is sharper on the smaller i-phone screen? Or maybe your system was better warmed up or suffering less RFI/EMI when you made the i-phone comparison? Or even, outside of your conscious appreciation, there was then a nice scent in the room ? Or the sun came out? Who knows?
All I can say is that technically it is not possible for only the choice of the device displaying Mosaic to affect the sound.