My understanding is that for audio the bit resolution of the A/D is crucial. Also looks like they have put together a system that not only can get a good sample but enough of them in some amount of time that it is usable and of some quality.

Not only that, audio CODECs have analog filters designed specifically for audio capture and reproduction, sometimes even configurable.

The advantage of having a cheap tiny board is that you can build a system like a polyphonic synth with very capable voices with relative ease. And since each one has inputs too, you can interconnect signals giving a lot of flexibility (aka modular synth).

A lot more power, yes, but also a lot more to worry about. It's a plus if you don't have to manage an entire OS. It would also probably need a lot more watts than this little board.