Read the quote again and explain it to me.
"AirPlay delivers better audio than the wireless airport express"
I'm fully aware of the capabilities of airport express, but how does the above make any sense. How does AirPlay deliver better audio than airport express? AirPlay isn't a device but a protocol that airport express uses.
If the op had said he thinks apple tv delivers delivers better audio than airport express, I could understand what he meant. Note I'm not saying that this is true, as I understand it apple tv resamples everything in a different way to airport express, possibly resulting in a audio difference, but I don't hear it between my airport express and apple tv.